Guide to the Secure Configuration of Ubuntu 16.04
Rules, Groups, and Values defined within the XCCDF Benchmark
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Configure System to Forward All Mail From Postmaster to The Root Account
Verify the administrators are notified in the event of an audit processing failure. Check that the "/etc/aliases" file has a defined value for "roo...Rule Medium Severity -
Configure System to Forward All Mail through a specific host
Set up a relay host that will act as a gateway for all outbound email. Edit the file <code>/etc/postfix/main.cf</code> to ensure that only the foll...Rule Medium Severity -
Configure Operating System to Protect Mail Server
The guidance in this section is appropriate for any host which is operating as a site MTA, whether the mail server runs using Sendmail, Postfix, or...Group -
Configure SSL Certificates for Use with SMTP AUTH
If SMTP AUTH is to be used, the use of SSL to protect credentials in transit is strongly recommended. There are also configurations for which it ma...Group -
Ensure Security of Postfix SSL Certificate
Create the PKI directory for mail certificates, if it does not already exist: <pre>$ sudo mkdir /etc/pki/tls/mail $ sudo chown root:root /etc/pki/t...Group -
Configure Postfix if Necessary
Postfix stores its configuration files in the directory /etc/postfix by default. The primary configuration file is/etc/postfix/main.cf.Group -
Configure Postfix Resource Usage to Limit Denial of Service Attacks
Edit <code>/etc/postfix/main.cf</code>. Edit the following lines to configure the amount of system resources Postfix can consume: <pre>default_proc...Group -
Control Mail Relaying
Postfix's mail relay controls are implemented with the help of the smtpd recipient restrictions option, which controls the restrictions placed on t...Group -
Enact SMTP Recipient Restrictions
To configure Postfix to restrict addresses to which it will send mail, see: <a href="http://www.postfix.org/SMTPD_ACCESS_README.html#danger">h...Group -
Enact SMTP Relay Restrictions
To configure Postfix to restrict addresses to which it will send mail, see: <a href="http://www.postfix.org/SMTPD_ACCESS_README.html#danger">h...Group -
Configure Trusted Networks and Hosts
Edit <code>/etc/postfix/main.cf</code>, and configure the contents of the <code>mynetworks</code> variable in one of the following ways: <ul> <li>I...Group -
Require SMTP AUTH Before Relaying from Untrusted Clients
SMTP authentication allows remote clients to relay mail safely by requiring them to authenticate before submitting mail. Postfix's SMTP AUTH uses a...Group -
NFS and RPC
The Network File System is a popular distributed filesystem for the Unix environment, and is very widely deployed. This section discusses the circ...Group -
Disable All NFS Services if Possible
If there is not a reason for the system to operate as either an NFS client or an NFS server, follow all instructions in this section to disable sub...Group -
Disable netfs if Possible
To determine if any network filesystems handled by netfs are currently mounted on the system execute the following command: <pre>$ mount -t nfs,nfs...Group -
Disable Network File Systems (netfs)
The netfs script manages the boot-time mounting of several types of networked filesystems, of which NFS and Samba are the most common. If these fil...Rule Unknown Severity -
Disable Services Used Only by NFS
If NFS is not needed, disable the NFS client daemons nfslock, rpcgssd, and rpcidmapd. <br><br> All of these daemons run with elevated privileges, a...Group -
Configure All Systems which Use NFS
The steps in this section are appropriate for all systems which run NFS, whether they operate as clients or as servers.Group -
Make Each System a Client or a Server, not Both
If NFS must be used, it should be deployed in the simplest configuration possible to avoid maintainability problems which may lead to unnecessary s...Group -
Configure NFS Services to Use Fixed Ports (NFSv3 and NFSv2)
Firewalling should be done at each host and at the border firewalls to protect the NFS daemons from remote access, since NFS servers should never b...Group
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