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XCCDF
Microsoft Outlook 2013 STIG
Microsoft Outlook 2013 STIG
An XCCDF Benchmark
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81 rules organized in 81 groups
DTOO111 - Enable IE Bind to Object
1 Rule
The Internet Explorer Bind to Object functionality must be enabled.
Medium Severity
Internet Explorer performs a number of safety checks before initializing an ActiveX control. It will not initialize a control if the kill bit for the control is set in the registry, or if the security settings for the zone in which the control is located do not allow it to be initialized. This functionality can be controlled separately for instances of Internet Explorer spawned by Office applications (for example, if a user clicks a link in an Office document or selects a menu option that loads a web page). A security risk could occur if potentially dangerous controls are allowed to load.
DTOO117 - Saved from URL
1 Rule
The Saved from URL mark must be selected to enforce Internet zone processing.
Medium Severity
Typically, when Internet Explorer loads a web page from a Universal Naming Convention (UNC) share that contains a Mark of the Web (MOTW) comment, indicating the page was saved from a site on the Internet, Internet Explorer runs the page in the Internet security zone instead of the less restrictive Local Intranet security zone. This functionality can be controlled separately for instances of Internet Explorer spawned by Office applications (for example, if a user clicks a link in an Office document or selects a menu option that loads a web page). If Internet Explorer does not evaluate the page for a MOTW, potentially dangerous code could be allowed to run.
DTOO123-Block Navigation to URL from Office
1 Rule
Navigation to URLs embedded in Office products must be blocked.
Medium Severity
To protect users from attacks, Internet Explorer usually does not attempt to load malformed URLs. This functionality can be controlled separately for instances of Internet Explorer spawned by Office applications (for example, if a user clicks a link in an Office document or selects a menu option that loads a web page). If Internet Explorer attempts to load a malformed URL, a security risk could occur.
DTOO129 - Block Pop-Ups
1 Rule
Links that invoke instances of Internet Explorer from within an Office product must be blocked.
Medium Severity
The Pop-up Blocker feature in Internet Explorer can be used to block most unwanted pop-up and pop-under windows from appearing. This functionality can be controlled separately for instances of Internet Explorer spawned by Office applications (for example, if a user clicks a link in an Office document or selects a menu option that loads a web page). If the Pop-up Blocker is disabled, disruptive and potentially dangerous pop-up windows could load and present a security risk.
DTOO272 - Content download from safe zones
1 Rule
Permit download of content from safe zones must be configured.
Medium Severity
By default, Outlook automatically downloads content from sites that are considered "safe," as defined in the Security tab of the Internet Options dialog box in Internet Explorer. This configuration could allow users to inadvertently download Web beacons that reveal their identity to spammers and other malicious people.
DTOO219 - Access to Published Calendars
1 Rule
Access restriction settings for published calendars must be configured.
Medium Severity
Users can share their calendars with others by publishing them to the Microsoft Office Online Calendar Sharing Services and to a server that supports the World Wide Web Distributed Authoring and Versioning (WebDAV) protocol. Office Online allows users to choose whether to restrict access to their calendars to people they invite, or allow unrestricted access to anyone who knows the URL to reach the calendar. DAV access restrictions can only be achieved through server and folder permissions, and might require the assistance of a server administrator to set up and maintain. If a calendar is visible to anyone on Office Online or third-party DAV servers, sensitive calendar information might be revealed.
DTOO224 - Email Recipient to Safe Sender List
1 Rule
Recipients of sent email must be unable to be added to the safe senders list.
Medium Severity
Users could send email messages to request that they be taken off a mailing list. If the email recipient is then automatically added to the Safe Senders List, future e mail messages from that address will no longer be sent to the users Junk email folder, even if it would otherwise be considered junk. By default, recipients of outgoing messages are not added automatically to individual users' Safe Senders Lists. However, users can change this configuration in the Outlook user interface.
DTOO234 - Active X One-Off Forms
1 Rule
ActiveX One-Off forms must be configured.
Medium Severity
Third-party ActiveX controls are not allowed to run in one-off forms in Outlook. This behavior can be changed so that Safe Controls (Microsoft Forms 2.0 controls and the Outlook Recipient and Body controls) are allowed in one-off forms, or so that all ActiveX controls are allowed to run.
DTOO246 - Scripts in One-Off Forms
1 Rule
Scripts in One-Off Outlook forms must be disallowed.
Medium Severity
Malicious code can be included within Outlook forms, and such code could be executed when users open the form. By default, Outlook does not run scripts in forms in which the script and the layout are contained within the message.
DTOO273 - Block Trusted Zones
1 Rule
IE Trusted Zones assumed trusted must be blocked.
Medium Severity
Malicious users can send HTML email messages with embedded Web beacons, which are pictures and other content from external servers that can be used to track whether specific recipients open the message. Viewing an email message that contains a Web beacon provides confirmation that the recipient's email address is valid, which leaves the recipient vulnerable to additional spam and harmful email. To reduce the risk from Web beacons, Outlook disables external content in email messages by default, unless the content is considered "safe" as determined by the check boxes in the Automatic Download section of the Trust Center. Depending on how these options are configured, safe content can include content in messages from addresses defined in the Safe Senders and Safe Recipients Lists used by the Junk email filter, content from SharePoint discussion boards, and content from websites in the Trusted sites zone in Internet Explorer. By default, Outlook considers trusted sites from Internet Explorer safe, and automatically downloads content from them, which could potentially include Web beacons.
DTOO236 - Add-In Trust Level
1 Rule
The Add-In Trust Level must be configured.
Medium Severity
Under normal circumstances the installed COM add-ins are applications that have been approved and intentionally deployed by the organization and therefore they should not pose a security threat. However, if malware has infected systems it is possible that the malware will use the COM add-in feature to perform unauthorized actions. This setting enforces the default configuration, and therefore is unlikely to cause significant usability issues for most users.
DTOO250 - Object Model Prompt for Address Book
1 Rule
Object Model Prompt behavior for programmatic address books must be configured.
Medium Severity
If an untrusted application accesses the address book, the application could gain access to sensitive data and potentially change that data. By default, when an untrusted application attempts to access the address book programmatically, Outlook relies on the setting configured in the "Programmatic Access" section of the Trust Center. This setting determines whether Outlook will warn users about programmatic access attempts. * Only when antivirus software is out of date or not running (the default setting) * Every time * Not at all If the "Not at all" option is selected, Outlook will silently grant programmatic access to any program that requests it, which could allow a malicious program to gain access to sensitive information. Note--This described default functionality assumes that the "Outlook Security Mode" Group Policy setting to ensure that Outlook security settings are configured by Group Policy has not been followed. If Group Policy security settings are used for Outlook, the "Programmatic Access" section of the Trust Center is not used. In this situation, the default is to prompt users based on computer security, which is the equivalent of the "Only when antivirus software is out of date or not running" option in the Trust Center, and the user experience is not affected.
DTOO241 - Demote Attachments to Level 2
1 Rule
Action to demote an EMail Level 1 attachment to Level 2 must be configured.
Medium Severity
Outlook uses two levels of security to restrict access to files attached to email messages or other items. Files with specific extensions can be categorized as Level 1 (users cannot view the file) or Level 2 (users can open the file after saving it to disk). Users can freely open files of types that are not categorized as Level 1 or Level 2. If users can demote Level 1 files to Level 2, they will be able to access potentially dangerous files after saving them to disk, which could allow malicious code to affect their computers or compromise the security of sensitive information.
DTOO254 - Object Model Prompt for Formula Property
1 Rule
Object Model Prompt behavior for accessing User Property Formula must be configured.
Medium Severity
A custom form in Outlook could be used to gain access to sensitive address book data and potentially to change that data. By default, when a user tries to bind an address information field to a combination or formula custom field in a custom form, Outlook relies on the setting configured in the "Programmatic Access" section of the Trust Center. This setting determines whether Outlook will warn users about programmatic access attempts: * Only when antivirus software is out of date or not running (the default setting) * Every time * Not at all If the "Not at all" option is selected, Outlook will silently grant programmatic access to any program that requests it, which could allow a malicious program to gain access to sensitive information. Note: This described default functionality assumes that the "Outlook Security Mode" Group Policy setting to ensure that Outlook security settings are configured by Group Policy has not been followed. If Group Policy security settings are used for Outlook, the "Programmatic Access" section of the Trust Center is not used. In this situation, the default is to prompt users based on computer security, which is the equivalent of the "Only when antivirus software is out of date or not running" option in the Trust Center, and the user experience is not affected.
DTOO253 - Object Model Prompt for Save As
1 Rule
Object Model Prompt behavior for the SaveAs method must be configured.
Medium Severity
If an untrusted application uses the Save As command to programmatically save an item, the application could add malicious data to a user's inbox, a public folder, or an address book. By default, when an untrusted application attempts to use the Save As command, Outlook relies on the setting configured in the "Programmatic Access" section of the Trust Center. This setting determines whether Outlook will warn users about programmatic access attempts: * Only when antivirus software is out of date or not running (the default setting) * Every time * Not at all If the "Not at all" option is selected, Outlook will silently grant programmatic access to any program that requests it, which could allow a malicious program to gain access to sensitive information. Note: This described default functionality assumes that the "Outlook Security Mode" Group Policy setting to ensure that Outlook security settings are configured by Group Policy has not been followed. If Group Policy security settings are used for Outlook, the "Programmatic Access" section of the Trust Center is not used. In this situation, the default is to prompt users based on computer security, which is the equivalent of the "Only when antivirus software is out of date or not running" option in the Trust Center, and the user experience is not affected.
DTOO251 - Object Model Prompt for Reading Address
1 Rule
Object Model Prompt behavior for programmatic access of user address data must be configured.
Medium Severity
If an untrusted application accesses the recipient fields, the application could gain access to sensitive data and potentially change that data. This could result in mail being sent to the wrong party. By default, when an untrusted application attempts to access recipient fields, Outlook relies on the setting configured in the "Programmatic Access" section of the Trust Center. This setting determines whether Outlook will warn users about programmatic access attempts: * Only when antivirus software is out of date or not running (the default setting) * Every time * Not at all If the "Not at all" option is selected, Outlook will silently grant programmatic access to any program that requests it, which could allow a malicious program to gain access to sensitive information. Note: This described default functionality assumes that the "Outlook Security Mode" Group Policy setting to ensure that Outlook security settings are configured by Group Policy has not been followed. If Group Policy security settings are used for Outlook, the "Programmatic Access" section of the Trust Center is not used. In this situation, the default is to prompt users based on computer security, which is the equivalent of the "Only when antivirus software is out of date or not running" option in the Trust Center, and the user experience is not affected.
DTOO252-Object Model Prompt for Meeting Response
1 Rule
Object Model Prompt behavior for Meeting and Task Responses must be configured.
Medium Severity
If an untrusted application programmatically responds to tasks or meeting requests, that application could impersonate a user response to the tasks or meeting requests with false information. By default, when an untrusted application attempts to respond to tasks or meeting requests programmatically, Outlook relies on the setting configured in the "Programmatic Access" section of the Trust Center. This setting determines whether Outlook will warn users about programmatic access attempts: • Only when antivirus software is out of date or not running (the default setting) • Every time • Not at all If the "Not at all" option is selected, Outlook will silently grant programmatic access to any program that requests it, which could allow a malicious program to gain access to sensitive information. Note This described default functionality assumes that you have not followed the recommendation to enable the "Outlook Security Mode" Group Policy setting to ensure that Outlook security settings are configured by Group Policy. If Group Policy security settings are used for Outlook, the "Programmatic Access" section of the Trust Center is not used. In this situation, the default is to prompt users based on computer security, which is the equivalent of the "Only when antivirus software is out of date or not running" option in the Trust Center, and the user experience is not affected.
DTOO249 - Object Model Prmpt for auto email send
1 Rule
Object Model Prompt for programmatic email send behavior must be configured.
Medium Severity
If an untrusted application programmatically sends email, that application could send mail that includes malicious code, impersonate a user, or launch a denial of service attack by sending a large volume of mail to a user or group of users. By default, when an untrusted application attempts to send mail programmatically, Outlook relies on the setting configured in the "Programmatic Access" section of the Trust Center. This setting determines whether Outlook will warn users about programmatic access attempts: * Only when antivirus software is out of date or not running (the default setting) * Every time * Not at all If the "Not at all" option is selected, Outlook will silently grant programmatic access to any program that requests it, which could allow a malicious program to gain access to sensitive information. Note--This described default functionality assumes that you have not followed the recommendation to enable the "Outlook Security Mode" Group Policy setting to ensure that Outlook security settings are configured by Group Policy. If Group Policy security settings are used for Outlook, the "Programmatic Access" section of the Trust Center is not used. In this situation, the default is to prompt users based on computer security, which is the equivalent of the "Only when antivirus software is out of date or not running" option in the Trust Center, and the user experience is not affected.
DTOO256 - Trusted Add-Ins Security
1 Rule
Trusted add-ins behavior for email must be configured.
Medium Severity
The Outlook object model includes entry points to access Outlook data, save data to specified locations, and send email messages, all of which can be used by malicious application developers. To help protect these entry points, the Object Model Guard warns users and prompts them for confirmation when untrusted code, including add-ins, attempts to use the object model to obtain email address information, store data outside of Outlook, execute certain actions, and send email messages. To reduce excessive security warnings when add-ins are used, administrators can specify a list of trusted add-ins that can access the Outlook object model silently, without raising prompts. This trusted add-in list should be treated with care, because a malicious add-in could access and forward sensitive information if added to the list.
DTOO237-Disable "remember password" on eMail Accts
1 Rule
The remember password for internet e-mail accounts must be disabled.
Medium Severity
As a security precaution, password caching for email Internet protocols such as POP3 or IMAP may lead to password discovery and eventually to data loss. An attacker that is able to access the users' profile may be able to acquire these cached passwords; they could then use this information to compromise the users' email accounts and other systems that use the same credentials.
DTOO243 - Level 1 Attachment prompt
1 Rule
The prompt to display level 1 attachments must be disallowed when closing an item.
Medium Severity
To protect users from viruses and other harmful files, Outlook uses two levels of security, designated Level 1 and Level 2, to restrict access to files attached to email messages or other items. Potentially harmful files can be classified into these two levels by file type extension, with all other file types considered safe. By default, Outlook completely blocks access to Level 1 files, and requires users to save Level 2 files to disk before opening them. If this configuration is changed, users will be able to open and execute potentially dangerous attachments, which can affect their computers or compromise the confidentiality, integrity, or availability of data.
DTOO242 - Level 1 Attachment Prompt on sending.
1 Rule
The prompt to display level 1 attachments must be disallowed when sending an item.
Medium Severity
To protect users from viruses and other harmful files, Outlook 2013 uses two levels of security, designated Level 1 and Level 2, to restrict access to files attached to e-mail messages or other items. Outlook completely blocks access to Level 1 files by default, and requires users to save Level 2 files to disk before opening them. Potentially harmful files can be classified into these two levels by file type extension, with all other file types considered safe. By default, when users attempt to send an item to which a level 1 file has been attached, Outlook warns them that the message contains a potentially unsafe attachment and that the recipient might not be able to access it. If this configuration is changed, Outlook will not display the warning when users send such items, which can cause users to lose access to important data.
DTOO283 - Dwnld articles as HTML attachments
1 Rule
Disabling download full text of articles as HTML must be configured.
Medium Severity
Many RSS feeds use messages that contain a brief summary of a larger message or an article with a link to the full content. Users can configure Outlook to automatically download the linked content as message attachments for individual RSS feeds. If a feed is frequently updated or typically contains very large messages and is not AutoArchived regularly, downloading full articles can cause the affected message store to become very large, which can affect the performance of Outlook. By default, Outlook does not automatically download the full text of RSS entries when retrieving feeds.
DTOO277 - Links in Email Messages
1 Rule
Hyperlinks in suspected phishing email messages must be disallowed.
Medium Severity
Outlook's Junk E-mail Filter evaluates each incoming message for possible spam or phishing content. Suspicious message detection is always turned on. By default, Outlook handles suspicious messages in two ways: * If the Junk E-mail Filter does not consider a message to be spam but does consider it to be phishing, the message is left in the Inbox but any links in the message are disabled and users cannot use the Reply and Reply All functionality. In addition, any attachments in the suspicious message are blocked. * If the Junk E-mail Filter considers the message to be both spam and phishing, the message is automatically sent to the Junk E-mail folder. Any message sent to the Junk E-mail folder is converted to plain text format and all links are disabled. In addition, the Reply and Reply All functionality is disabled and any attachments in the message are blocked. The InfoBar alerts users to this change in functionality. If users are certain that a message is legitimate, they can click the InfoBar and enable the links in the message. Users can change the way Outlook handles phishing messages in the Junk E-mail Options dialog box by clearing the Disable links and other functionality in phishing messages (Recommended) check box. If this check box is cleared, Outlook will not disable links in suspected phishing messages unless they are classified as junk email, which could allow users to disclose confidential information to malicious websites.
DTOO279 - Enable RPC Encryption
1 Rule
RPC encryption between Outlook and Exchange server must be enforced.
Medium Severity
The remote procedure call (RPC) communication channel between an Outlook client computer and an Exchange server is not encrypted. If a malicious individual is able to eavesdrop on the network traffic between Outlook and the server, they might be able to access confidential information.
DTOO221 - Junk Mail UI
1 Rule
Junk Mail UI must be configured.
Medium Severity
The Junk E-mail Filter in Outlook is designed to intercept the most obvious junk email, or spam, and send it to users' Junk E-mail folders. The filter evaluates each incoming message based on several factors, including the time when the message was sent and the content of the message. The filter does not single out any particular sender or message type, but instead analyzes each message based on its content and structure to discover whether or not it is probably spam. By default, the Junk E-mail Filter in Outlook is enabled. If this configuration is changed, users can receive large amounts of junk email in their Inboxes, which could make it difficult for them to work with business-related email messages.
DTOO274 - Internet with Safe Zones
1 Rule
Internet with Safe Zones for Picture Download must be disabled.
Medium Severity
Malicious email senders can send HTML email messages with embedded Web beacons, which are pictures and other content from external servers that can be used to track whether recipients open the messages. Viewing email messages that contain Web beacons provides confirmation that the recipient's email address is valid, which leaves the recipient vulnerable to additional spam and harmful email. By default, Outlook does not download external content in HTML email messages from untrusted senders via the Internet. If this configuration is changed, Outlook will display external content in all HTML email messages received from the Internet, which could include Web beacons.
DTOO275 - Incl. Intranet with Safe Zone
1 Rule
Intranet with Safe Zones for automatic picture downloads must be configured.
Medium Severity
Malicious email senders can send HTML email messages with embedded Web beacons, which are pictures and other content from external servers that can be used to track whether recipients open the messages. Viewing email messages with Web beacons in them provides confirmation that the recipient's email address is valid, which leaves the recipient vulnerable to additional spam and harmful email. By default, Outlook does not download external content in HTML email messages from untrusted senders over the local intranet. If this configuration is changed, Outlook will display external content in all HTML email messages received via the local intranet, which could include Web beacons.
DTOO240 - Level 1 Attachments
1 Rule
The ability to display level 1 attachments must be disallowed.
Medium Severity
To protect users from viruses and other harmful files, Outlook uses two levels of security, designated Level 1 and Level 2, to restrict access to files attached to email messages or other items. Potentially harmful files can be classified into these two levels by file type extension, with all other file types considered safe. By default, Outlook completely blocks access to Level 1 files, and requires users to save Level 2 files to disk before opening them. If this configuration is changed, users will be able to open and execute potentially dangerous attachments, which can affect their computers or compromise the confidentiality, integrity, or availability of data.
DTOO270 - External Pictures & content
1 Rule
External content and pictures in HTML email must be displayed.
Medium Severity
Malicious email senders can send HTML email messages with embedded Web beacons, which are pictures and other content from external servers that can be used to track whether specific recipients open the message. Viewing an email message that contains a Web beacon provides confirmation that the recipient's email address is valid, which leaves the recipient vulnerable to additional spam and harmful email. By default, Outlook does not download external content in HTML email and RSS items unless the content is considered safe. Content that Outlook can be configured to consider safe includes: * Content in email messages from senders and to recipients defined in the Safe Senders and Safe Recipients lists. * Content from websites in Internet Explorer's Trusted Sites security zone. * Content in RSS items. * Content from SharePoint Discussion Boards. Users can control what content is considered safe by changing the options in the Automatic Download section of the Trust Center. If Outlook's default blocking configuration is overridden, in the Trust Center or by some other method, Outlook will display external content in all HTML email messages, including any that include Web beacons.
DTOO227 - Digital Signature handling
1 Rule
The ability to add signatures to email messages must be allowed.
Medium Severity
Outlook users can create and use signatures in email messages. Users can add signatures to messages manually, and can also configure Outlook to automatically append signatures to new messages, to replies and forwards, or to all three. Signatures typically include details such as the user's name, title, phone numbers, and office location. When an organization has policies that govern the distribution of this kind of information, using signatures might cause some users to inadvertently violate these policies.
DTOO230 - No fldr home pages / non-default stores
1 Rule
Folders in non-default stores, set as folder home pages, must be disallowed.
Medium Severity
Outlook allows users to designate Web pages as home pages for personal or public folders. When a user clicks on a folder, Outlook displays the home page the user has assigned to it. Although this feature provides the opportunity to create powerful public folder applications, scripts can be included on Web pages that access the Outlook object model, which exposes users to security risks. By default, Outlook does not allow users to define folder home pages for folders in non-default stores. If this configuration is changed, users can create and access dangerous folder home pages for Outlook data files (.pst) and other non-default stores, which can compromise the security of the users' data.
DTOO233 - OOM scripts for Public Folders
1 Rule
Outlook Object Model scripts must be disallowed to run for public folders.
Medium Severity
In Outlook, folders can be associated with custom forms or folder home pages that include scripts that access the Outlook object model. These scripts can add functionality to the folders and items contained within, but dangerous scripts can pose security risks. By default, Outlook allows scripts included in custom forms or folder home pages for public folders to execute. If users inadvertently run dangerous scripts when using public folders, their computers or data could be at risk.
DTOO232 - OOM scripts for Shared Folders
1 Rule
Outlook Object Model scripts must be disallowed to run for shared folders.
Medium Severity
In Outlook, folders can be associated with custom forms or folder home pages that include scripts that access the Outlook object model. These scripts can add functionality to the folders and items contained within, but dangerous scripts can pose security risks. By default, Outlook does not allow scripts included in custom forms or folder home pages for shared folders to execute. If this configuration is changed, users can inadvertently run dangerous scripts when using shared folders, which can put their computers or data at risk.
DTOO285 - Internet Calendar Integration
1 Rule
Internet calendar integration in Outlook must be disabled.
Medium Severity
The Internet Calendar feature in Outlook enables users to publish calendars online (using the webcal:// protocol) and subscribe to calendars that others have published. When users subscribe to an Internet calendar, Outlook queries the calendar at regular intervals and downloads any changes as they are posted. By default, Outlook allows users to subscribe to Internet calendars. When an organization has policies that govern the use of external resources such as Internet calendars, this feature will enable users to violate those policies.
DTOO269 - Attachments to Secure Temporary Folder
1 Rule
Attachments using generated name for secure temporary folders must be configured.
Medium Severity
The Secure Temporary Files folder is used to store attachments when they are opened in email. By default, Outlook generates a random name for the Secure Temporary Files folder and saves it in the Temporary Internet Files folder. This setting can be used to designate a specific path and folder to use as the Secure Temporary Files folder. This configuration is not recommended, because it means that all users will have temporary Outlook files in the same predictable location, which is not as secure. If the name of this folder is well known, a malicious user or malicious code might target this location to try and gain access to attachments.
DTOO280 - Authentication w/Exchange Svr
1 Rule
Outlook must be configured to force authentication when connecting to an Exchange server.
Medium Severity
Exchange Server supports the Kerberos authentication protocol and NTLM for authentication. The Kerberos protocol is the more secure authentication method and is supported on Windows 2000 Server and later versions. NTLM authentication is supported in pre-Windows 2000 environments. When authentication is enabled, Outlook will attempt to authenticate using the Kerberos authentication protocol, if it cannot (because no Windows 2000 or later domain controllers are available), it will authenticate using NTLM, ensuring a more secure authentication to the Exchange server.
DTOO284 - Auto download attachments Internet Cal
1 Rule
Automatic download of Internet Calendar appointment attachments must be disallowed.
Medium Severity
Files attached to Internet Calendar appointments could contain malicious code that could be used to compromise a computer. By default, Outlook does not download attachments when retrieving Internet Calendar appointments.
DTOO271 - Auto Download from Safe lists
1 Rule
Automatic download content for email in Safe Senders list must be disallowed.
Medium Severity
Malicious email senders can send HTML email messages with embedded Web beacons, or pictures and other content from external servers that can be used to track whether specific recipients have opened a message. Viewing an email message that contains a Web beacon provides confirmation that the recipient's email address is valid, which leaves the recipient vulnerable to additional spam and harmful email. To help protect users from Web beacons, Outlook can be configured to automatically block the display of external content in email messages. However, because this configuration could block desirable content from display, Outlook can also be configured to automatically display external content in any messages sent by people who are listed in users' Safe Senders Lists or Safe Recipients Lists. By default, Outlook automatically displays external content in email messages from people listed in users' Safe Senders Lists or Safe Recipients Lists, and automatically blocks external content in other messages. If a malicious sender is accidentally added to a user's Safe Senders List or Safe Recipients List, Outlook will display external content in all email messages from the malicious sender, which could include Web beacons.
DTOO229 - Make Outlook the default program
1 Rule
Outlook must be enforced as the default email, calendar, and contacts program.
Medium Severity
Outlook is made the default program for email, contacts, and calendar services when it is installed, although users can designate other programs as the default programs for these services. If another application is used to provide these services and the organization does not ensure the security of that application, it could be exploited to gain access to sensitive information or launch other malicious attacks. When an organization has policies that govern the use of personal information management software, allowing users to change the default configuration could enable them to violate such policies.
DTOO260 - SMime message formats
1 Rule
Message formats must be set to use SMime.
Medium Severity
Email typically travels over open networks and is passed from server to server. Messages are therefore vulnerable to interception, and attackers might read or alter their contents. It is therefore important to have a mechanism for signing messages and providing end-to-end encryption. Outlook supports three formats for encrypting and signing messages: S/MIME, Exchange, and Fortezza. By default, Outlook only uses S/MIME to encrypt and sign messages. When an organization has policies that mandate the use of specific encryption formats, allowing users to choose freely between these formats could cause them to violate such policies.
DTOO268 - Missing Root Certificates
1 Rule
Missing Root Certificates warning must be enforced.
Medium Severity
When Outlook accesses a certificate, it validates that it can trust the certificate by examining the root certificate of the issuing CA. If the root certificate can be trusted, then certificates issued by the CA can also be trusted. If Outlook cannot find the root certificate, it cannot validate that any certificates issued by that CA can be trusted. An attacker may compromise a root certificate and then remove the certificate in an attempt to conceal the attack. By default, Outlook displays a warning message when a CRL is not available.
DTOO239 - Outlook Security Mode
1 Rule
Outlook Security Mode must be configured to use Group Policy settings.
Medium Severity
If users can configure security themselves, they might choose levels of security that leave their computers vulnerable to attack. By default, Outlook users can configure security for themselves, and Outlook ignores any security-related settings that are configured in Group Policy.
DTOO228 - Plain Text Options
1 Rule
Plain Text Options for outbound email must be configured.
Medium Severity
If outgoing mail is formatted in certain ways, for example, if attachments are encoded in UUENCODE format, attackers might manipulate the messages for their own purposes. If UUENCODE formatting is used, an attacker could manipulate the encoded attachment to bypass content filtering software. Outlook 2013 automatically wraps plain text messages and uses the standard MIME format to encode attachments in plain text messages. However, these settings can be altered to allow email to be read in plain text email programs that use a nonstandard line length or that cannot process MIME attachments.
DTOO217 - Prevent publishing to DAV Servers
1 Rule
Publishing to a Web Distributed and Authoring (DAV) server must be prevented.
Medium Severity
Outlook users can share their calendars with others by publishing them to a server that supports the World Wide Web Distributed Authoring and Versioning (WebDAV) protocol. Unlike the Microsoft Office Online Calendar Sharing Service, which allows users to manage other people's access to their calendars, DAV access restrictions can only be accomplished through server and folder permissions, and might require the assistance of the server administrator to set up and maintain. If these permissions are not managed properly, unauthorized individuals could access sensitive information.
DTOO216 - Publishing to Office Online
1 Rule
Publishing calendars to Office Online must be prevented.
Medium Severity
Outlook users can share their calendars with selected others by publishing them to the Microsoft Office Outlook Calendar Sharing Service. Users can control who can view their calendar and at what level of detail. When an organization has policies that govern access to external resources such as Office Online, allowing users to publish their calendars will enable them to violate those policies.
DTOO238 - Prev't users customizing security set
1 Rule
Users customizing attachment security settings must be prevented.
Medium Severity
All installed trusted COM addins can be trusted. Exchange settings for the addins still override if present and this option is selected.
DTOO214 - Read EMail as plain text
1 Rule
Read EMail as plain text must be enforced.
Medium Severity
Outlook can display email messages and other items in three formats: plain text, Rich Text Format (RTF), and HTML. By default, Outlook displays email messages in whatever format they were received in.
DTOO215 - Read signed EMail as plain text
1 Rule
Read signed email as plain text must be enforced.
Medium Severity
Outlook can display email messages and other items in three formats: plain text, Rich Text Format (RTF), and HTML. By default, Outlook displays digitally signed email messages in the format they were received in.
DTOO244 - Lvl 1 File extensions
1 Rule
Level 1 file extensions must be blocked and not removed.
Medium Severity
Malicious code is often spread through e-mail. Some viruses have the ability to send copies of themselves to other people in the victim's Address Book or Contacts list, and such potentially harmful files can affect the computers of unwary recipients.
DTOO245 - Lvl 2 File Extensions
1 Rule
Level 2 file extensions must be blocked and not removed.
Medium Severity
Malicious code is often spread through email. Some viruses have the ability to send copies of themselves to other people in the victim's Address Book or Contacts list, and such potentially harmful files can affect the computers of unwary recipients. Outlook uses two levels of security to restrict users' access to files attached to email messages or other items. Files with specific extensions can be categorized as Level 1 (users cannot view the file) or Level 2 (users can open the file after saving it to disk). Users can freely open files of types that are not categorized as Level 1 or Level 2. By default, Outlook classifies a number of potentially harmful file types as Level 1. (See Attachment file types restricted by Outlook for the complete list.) Outlook does not classify any file types as Level 2 by default, so this setting is not particularly useful in isolation. Typically, if there are extensions on the Level 2 list they would have been added by using the "Add file extensions to block as Level 2" setting, through which they can be removed. The combined lists of blocked and restricted file extensions that Outlook uses are actually built by combining various policies together. If a machine policy classifies an extension as Level 2, this setting could be used to remove the extension from the list in some situations. As with Level 1 extensions, though, removing restrictions on potentially dangerous extensions can make it easier for users to open dangerous files, which can significantly reduce security.
DTOO218 - Calendar details published by users
1 Rule
Level of calendar details that a user can publish must be restricted.
Medium Severity
Outlook users can share their calendars with selected others by publishing them to the Microsoft Office Outlook Calendar Sharing Service. Users can choose from three levels of detail: * Availability only. Authorized visitors will see the user's time marked as Free, Busy, tentative, or Out of Office, but will not be able to see the subjects or details of calendar items. * Limited details. Authorized visitors can see the user's availability and the subjects of calendar items only. They will not be able to view the details of calendar items. Optionally, users can allow visitors to see the existence of private items. * Full details. Authorized visitors can see the full details of calendar items. Optionally, users can allow visitors to see the existence of private items and to access attachments within calendar items. If users are allowed to publish limited or full details, sensitive information in their calendars could become exposed to parties who are not authorized to have that information.
DTOO220 - Upload methods
1 Rule
Upload method for publishing calendars to Office Online must be restricted.
Medium Severity
When users publish their calendar to Microsoft Office Online using the Microsoft Office Outlook Calendar Sharing Service, Outlook updates the calendars online at regular intervals unless they click Advanced and select Single Upload: Updates will not be uploaded from the Published Calendar Settings dialog box. When an organization has policies that govern the use of external resources such as Microsoft Office Online, allowing Outlook to publish calendar updates automatically might violate those policies.
DTOO267 - Retrieving CRLs - Outlook
1 Rule
Retrieving of CRL data must be set for online action.
Medium Severity
This policy setting controls how Outlook retrieves Certificate Revocation Lists to verify the validity of certificates. Certificate revocation lists (CRLs) are lists of digital certificates that have been revoked by their controlling certificate authorities (CAs), typically because the certificates were issued improperly or their associated private keys were compromised.
DTOO262 - FIPS compliant mode
1 Rule
Run in FIPS compliant mode must be enforced.
Medium Severity
Outlook can run in a mode that complies with Federal Information Processing Standards (FIPS), a set of standards published by the National Institute of Standards and Technology (NIST) for use by non-military United States government agencies and by government contractors. By default, Outlook does not run in FIPS-compliant mode. Organizations that do business with the U.S. government but do not run Outlook in FIPS-compliant mode risk violating the government's rules regarding the handling of sensitive information.
DTOO257 - No S/Mime interop w/ external clients
1 Rule
S/Mime interoperability with external clients for message handling must be configured.
Medium Severity
In some situations, administrators might wish to use an external program, such as an add-in, to handle S/MIME message decryption. If your organization works with encrypted messages that the decryption functionality in Outlook cannot handle appropriately, this setting can be used to configure Outlook to hand S/MIME messages off to an external program for decryption. If no external program has been authorized however, misconfiguring this setting could allow unauthorized and potentially dangerous programs to handle encrypted messages, which could compromise security.
DTOO266 - S/Mime receipt requests
1 Rule
Automatic sending s/Mime receipt requests must be disallowed.
Medium Severity
Incoming signed or encrypted messages might include S/MIME receipt requests. S/MIME receipts provide confirmation that messages are received unaltered, and can include information about who opened the message and when it was opened. By default, when users open messages with attached receipt requests, Outlook prompts them to decide whether to send a receipt to the sender with information about the identity of the user who opened the message and the time it was opened. If Outlook cannot send the receipt, the user is still allowed to open the message. In some situations, allowing Outlook to automatically send receipt requests could cause sensitive information to be divulged to unauthorized individuals.
DTOO276 - Security settings for macros
1 Rule
Always warn on untrusted macros must be enforced.
Medium Severity
To protect users from dangerous code, the Outlook default configuration disables all macros that are not trusted, including unsigned macros, macros with expired or invalid signatures, and macros with valid signatures from publishers who are not on users' Trusted Publishers lists. The default configuration also allows macros that are signed by trusted publishers to run automatically without notifying users, which could allow dangerous code to run.
DTOO264 - Clear signed messages
1 Rule
Send all signed messages as clear signed messages must be configured.
Medium Severity
When users sign email messages with their signing certificate and send them, Outlook uses the sender's private key to encrypt the digital signature but sends the messages as clear text, unless they are encrypted separately. If users change this functionality by clearing the "Send clear text signed message when sending signed messages" option in the email Security section of the Trust Center, any recipients who are unable to access or use the sender's digital certificate will not be able to read the email messages.
DTOO247 - Custom OOM Action Exe. Prompt
1 Rule
Custom Outlook Object Model (OOM) action execution prompts must be configured.
Medium Severity
Custom actions add functionality to Outlook that can be triggered as part of a rule. Among other possible features, custom actions can be created that reply to messages in ways that circumvent the Outlook model's programmatic send protections. By default, when Outlook or another program initiates a custom action using the Outlook object model, users are prompted to allow or reject the action. If this configuration is changed, malicious code can use the Outlook object model to compromise sensitive information or otherwise cause data and computing resources to be at risk.
DTOO265 - Signature Warnings
1 Rule
Warning about invalid signatures must be enforced.
Medium Severity
If users open email messages that include invalid digital signatures, Outlook displays a warning dialog box. Users can decide whether they want to be warned about invalid signatures in the future. If users are not notified about invalid signatures, they might be prevented from detecting a fraudulent signature sent by a malicious person.
DTOO281 - Sync RSS Feeds w/Common List
1 Rule
RSS feed synchronization with Common Feed List must be disallowed.
Medium Severity
The Common Feed list is a hierarchical set of RSS feeds to which clients such as Outlook 2013, the Feeds list in Internet Explorer, and the Feed Headlines Sidebar gadget in Windows Vista can subscribe. If Outlook subscribes to a very large feed list, performance and availability can be affected, especially if Outlook is configured to download full RSS message bodies or if the feed list is not AutoArchived regularly. By default, Outlook maintains its own list of feeds and does not automatically subscribe to RSS feeds that are added to the Common Feed List.
DTOO223 - Trust EMail from Contacts
1 Rule
Trust EMail from senders in receivers contact list must be enforced.
Medium Severity
Email addresses in users' Contacts list are treated as safe senders for purposes of filtering junk email. If this configuration is changed, email from users' Contacts might be misclassified as junk and cause important information to be lost.
DTOO282 - RSS Feeds
1 Rule
RSS Feeds must be disallowed.
Medium Severity
Users can subscribe to RSS feeds from within Outlook and read RSS items like email messages. If an organization has policies that govern the use of external resources such as RSS feeds, allowing users to subscribe to the RSS feed in Outlook will enable them to violate those policies.
DTOO231 - Unicode use when dragging Email
1 Rule
Dragging Unicode email messages to file system must be disallowed.
Medium Severity
When users drag email messages from Outlook to a Windows Explorer window or to their Desktop, Outlook creates an .msg file using the native character encoding format for the configured locale (the so-called "ANSI" format). If this setting is Enabled, Outlook uses the Unicode character encoding standard to create the message file, which preserves special characters in the message. However, Unicode text is vulnerable to homograph attacks, in which characters are replaced by different but similar-looking characters. For example, the Cyrillic letter "?" (U+0430) appears identical to the Latin letter "a" (U+0061) in many typefaces, but is actually a different character. Homographs can be used in "phishing" attacks to convince victims to visit fraudulent websites and enter sensitive information.
DTOO286 - Disable User Entries to Server list
1 Rule
User Entries to Server List must be disallowed.
Medium Severity
If users are able to manually enter the addresses of servers that are not approved by the organization, they could use servers that do not meet your organization's information security requirements, which could cause sensitive information to be at risk. By default, when users create a meeting workspace, they can choose a server from a default list provided by administrators or manually enter the address of a server that is not listed.
DTOO126 - Add-on Management
1 Rule
Add-on Management functionality must be allowed.
Medium Severity
Internet Explorer add-ons are pieces of code, run in Internet Explorer, to provide additional functionality. Rogue add-ons may contain viruses or other malicious code. Disabling or not configuring this setting could allow malicious code or users to become active on user computers or the network. For example, a malicious user can monitor and then use keystrokes users type into Internet Explorer. Even legitimate add-ons may demand resources, compromising the performance of Internet Explorer, and the operating systems for user computers.
DTOO209 - Zone Elevation Protection
1 Rule
Protection from zone elevation must be enforced.
Medium Severity
Internet Explorer places restrictions on each web page users can use the browser to open. Web pages on a user's local computer have the fewest security restrictions and reside in the Local Machine zone, making this security zone a prime target for malicious users and code. Disabling or not configuring this setting could allow pages in the Internet zone to navigate to pages in the Local Machine zone to then run code to elevate privileges. This could allow malicious code or users to become active on user computers or the network.
DTOO211 - Restrict ActiveX Install
1 Rule
ActiveX installs must be configured for proper restrictions.
Medium Severity
Microsoft ActiveX controls allow unmanaged, unprotected code to run on the user computers. ActiveX controls do not run within a protected container in the browser like the other types of HTML or Microsoft Silverlight-based controls. Disabling or not configuring this setting does not block prompts for ActiveX control installations and these prompts display to users. This could allow malicious code to become active on user computers or the network.
DTOO132 - Restrict File Download
1 Rule
File Downloads must be configured for proper restrictions.
Medium Severity
Disabling this setting allows websites to present file download prompts via code without the user specifically initiating the download. User preferences may also allow the download to occur without prompting or interaction with the user. Even if Internet Explorer prompts the user to accept the download, some websites abuse this functionality. Malicious websites may continually prompt users to download a file or present confusing dialog boxes to trick users into downloading or running a file. If the download occurs and it contains malicious code, the code could become active on user computers or the network.
DTOO124 - Scripted Window Security
1 Rule
Scripted Window Security must be enforced.
Medium Severity
Malicious websites often try to confuse or trick users into giving a site permission to perform an action allowing the site to take control of the users' computers in some manner. Disabling or not configuring this setting allows unknown websites to: -Create browser windows appearing to be from the local operating system. -Draw active windows displaying outside of the viewable areas of the screen capturing keyboard input. -Overlay parent windows with their own browser windows to hide important system information, choices or prompts.
DTOO313 - Automatically download enclosures
1 Rule
Automatically downloading enclosures on RSS must be disallowed.
Medium Severity
This policy setting controls Outlook's ability to automatically download enclosures on RSS items.
DTOO344 - Outlook Rich Text options
1 Rule
Outlook Rich Text options must be set for converting to plain text format.
Medium Severity
Outlook automatically converts RTF formatted messages that are sent over the Internet to HTML format, so that the message formatting is maintained and attachments are received. This setting controls how Outlook sends Rich Text Format (RTF) messages to Internet recipients.
DTOO314 - Set message format
1 Rule
Default message format must be set to use Plain Text.
Medium Severity
Outlook uses HTML as the default email format. HTML format poses a security risk by embedding information into the email itself, which could allow for release of sensitive information. If a user attempted to insert an HTML link into an email message, the link itself may direct to a malicious website. By sending in that format, the recipient would be subject to becoming infected by the malicious website.
DTOO315 - Outlook Security settings
1 Rule
Outlook must be configured not to prompt users to choose security settings if default settings fail.
Medium Severity
This policy prompts the user to choose security settings if default settings fail, but allowing users to select their own security settings would result in inconsistent enforcement in the organization and the likelihood of nonsecure settings being applied.
DTOO316 - Minimum encryption settings
1 Rule
Outlook minimum encryption key length settings must be set.
Medium Severity
This setting allows the minimum key length for an encrypted email message to be configured.
DTOO317 - Signed/encrypted messages
1 Rule
Replies or forwards to signed/encrypted messages must be signed/encrypted.
Medium Severity
This setting controls whether replies and forwards to signed/encrypted mail should also be signed/encrypted.
DTOO320 - Check e-mail address against certificate
1 Rule
Check e-mail addresses against addresses of certificates being used must be disallowed.
Medium Severity
This policy setting controls whether Outlook verifies the user's email address with the address associated with the certificate used for signing.
DTOO424 - Disable weather bar in Outlook
1 Rule
The use of the weather bar in Outlook must be disabled
Medium Severity
The Weather Bar in Outlook displays weather conditions and forecast for a geographic location. By default, Outlook uses weather data provided by MSN Weather. The Weather Bar supports third-party weather data web services that follow a defined protocol to communicate with Outlook. As long as a third-party weather data service supports this protocol, users can choose that weather data service to provide weather data in the Weather Bar. Since the Weather Bar communicates to external, commercial weather sites, enabling it introduces the possibility of connections to malicious sites that could download malware into the environment.
DTOO425 - Disable Internet and network path into hyperlinks
1 Rule
Text in Outlook that represents Internet and network paths must not be automatically turned into hyperlinks.
Medium Severity
The ability of Outlook to automatically turn text that represents Internet and network paths into hyperlinks would allow users to click on those hyperlinks in email message and access malicious or otherwise harmful websites.
DTOO104 - Disable user name and password
1 Rule
Disabling of user name and password syntax from being used in URLs must be enforced.
Medium Severity
The Uniform Resource Locator (URL) standard allows user authentication to be included in URL strings in the form http://username:password@example.com. A malicious user might use this URL syntax to create a hyperlink that appears to open a legitimate website but actually opens a deceptive (spoofed) website. For example, the URL http://www.wingtiptoys.com@example.com appears to open http://www.wingtiptoys.com but actually opens http://example.com. To protect users from such attacks, Internet Explorer usually blocks any URLs using this syntax. This functionality can be controlled separately for instances of Internet Explorer spawned by Office applications (for example, if a user clicks a link in an Office document or selects a menu option that loads a web page). If user names and passwords in URLs are allowed, users could be diverted to dangerous web pages, which would pose a security risk.