Domain Name System (DNS) Security Requirements Guide
Rules, Groups, and Values defined within the XCCDF Benchmark
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The DNS implementation must limit the number of concurrent sessions for zone transfers to the number of secondary name servers.
Limiting the number of concurrent sessions reduces the risk of Denial of Service (DoS) to the DNS implementation. Name servers do not have direct user connections but accept client connections fo...Rule Medium Severity -
The DNS server implementation must produce audit records containing information to establish what type of events occurred.
Auditing and logging are key components of any security architecture. It is essential for security personnel to know what is being performed on the system, where an event occurred, when an event oc...Rule Medium Severity -
The DNS server implementation must produce audit records containing information to establish when (date and time) the events occurred.
Without establishing when events occurred, it is impossible to establish, correlate, and investigate the events relating to an incident. Associating event types with detected events in the applic...Rule Medium Severity -
The DNS server implementations audit records must be backed up at least every seven days onto a different system or system component than the system or component being audited.
Protection of log data includes assuring log data is not accidentally lost or deleted. Backing up audit records to a different system or onto separate media than the system being audited on a defin...Rule Medium Severity -
The DNS server implementation must be configured to prohibit or restrict unapproved ports and protocols.
In order to prevent unauthorized connection of devices, unauthorized transfer of information, or unauthorized tunneling (i.e., embedding of data types within data types), organizations must disable...Rule Medium Severity -
Read/Write access to the key file must be restricted to the account that runs the name server software only.
To enable zone transfer (requests and responses) through authenticated messages, it is necessary to generate a key for every pair of name servers. The key can also be used for securing other transa...Rule Medium Severity -
Signature generation using the KSK must be done off-line, using the KSK-private stored off-line.
Security-relevant information is any information within information systems that can potentially impact the operation of security functions or the provision of security services in a manner that co...Rule Medium Severity -
A DNS server implementation must provide additional data origin artifacts along with the authoritative data the system returns in response to external name/address resolution queries.
The underlying feature in the major threat associated with DNS query/response (i.e., forged response or response failure) is the integrity of DNS data returned in the response. The security objecti...Rule Medium Severity -
The DNS server implementation must enforce approved authorizations for controlling the flow of information between DNS servers and between DNS servers and DNS clients based on DNSSEC policies.
A mechanism to detect and prevent unauthorized communication flow must be configured or provided as part of the system design. If information flow is not enforced based on approved authorizations, ...Rule Medium Severity -
A DNS server implementation must provide the means to enable verification of a chain of trust among parent and child domains (if the child supports secure resolution services).
If name server replies are invalid or cannot be validated, many networking functions and communication would be adversely affected. With DNS, the presence of Delegation Signer (DS) records associat...Rule Medium Severity -
The DNS implementation must protect the authenticity of communications sessions for queries.
The underlying feature in the major threat associated with DNS query/response (i.e., forged response or response failure) is the integrity of DNS data returned in the response. An integral part of ...Rule Medium Severity -
The DNS server implementation must fail to a secure state if system initialization fails, shutdown fails, or aborts fail.
Failure to a known safe state helps prevent systems from failing to a state that may cause loss of data or unauthorized access to system resources. Applications or systems that fail suddenly and wi...Rule Medium Severity -
In the event of a system failure, the DNS server implementation must preserve any information necessary to determine cause of failure and any information necessary to return to operations with least disruption to mission processes.
Failure to a known state can address safety or security in accordance with the mission/business needs of the organization. Failure to a known secure state helps prevent a loss of confidentiality, i...Rule Medium Severity -
The DNS server implementation must protect the confidentiality and integrity of secret/private cryptographic keys at rest and the integrity of DNS information at rest.
Information at rest refers to the state of information when it is located on a secondary storage device within an organizational information system. Mobile devices, laptops, desktops, and storage d...Rule Medium Severity -
The DNS server implementation must prevent unauthorized and unintended information transfer via shared system resources.
Preventing unauthorized information transfers mitigates the risk of information, including encrypted representations of information, produced by the actions of prior users/roles (or the actions of ...Rule Medium Severity -
The DNS server implementation must restrict the ability of individuals to use the DNS server to launch Denial of Service (DoS) attacks against other information systems.
A DoS is a condition where a resource is not available for legitimate users. When this occurs, the organization either cannot accomplish its mission or must operate at degraded capacity. Individua...Rule Medium Severity -
The DNS server implementation must manage excess capacity, bandwidth, or other redundancy to limit the effects of information flooding types of Denial of Service (DoS) attacks.
A DoS is a condition when a resource is not available for legitimate users. When this occurs, the organization either cannot accomplish its mission or must operate at degraded capacity. In the ca...Rule Medium Severity -
The DNS server implementation must check the validity of all data inputs except those specifically identified by the organization.
Invalid user input occurs when a user inserts data or characters into an application's data entry fields and the application is unprepared to process that data. This results in unanticipated applic...Rule Medium Severity -
The DNS server implementation must, when a component failure is detected, activate a notification to the system administrator.
Predictable failure prevention requires organizational planning to address system failure issues. If components key to maintaining systems security fail to function, the system could continue opera...Rule Medium Severity -
The DNS server implementation must be configured to generate audit records for failed security verification tests so that the ISSO and ISSM can be notified of the failures.
Security function is defined as the hardware, software, and/or firmware of the information system responsible for enforcing the system security policy and supporting the isolation of code and data ...Rule Medium Severity -
The DNS server implementation must strongly bind the identity of the DNS server with the DNS information.
Weakly bound credentials can be modified without invalidating the credential; therefore, non-repudiation can be violated. This requirement supports audit requirements that provide organizational p...Rule Medium Severity -
The DNS server implementation must provide the means for authorized individuals to determine the identity of the source of the DNS server-provided information.
Without a means for identifying the individual that produced the information, the information cannot be relied upon. Identifying the validity of information may be delayed or deterred. This requir...Rule Medium Severity -
The DNS server implementation must validate the binding of the other DNS servers identity to the DNS information for a server-to-server transaction (e.g., zone transfer).
Validation of the binding of the information prevents the modification of information between production and review. The validation of bindings can be achieved, for example, by the use of cryptogra...Rule Medium Severity -
In the event of an error when validating the binding of another DNS servers identity to the DNS information, the DNS server implementation must log the event and send notification to the DNS administrator.
Failing to act on the validation errors may result in the use of invalid, corrupted, or compromised information. The validation of bindings can be achieved, for example, by the use of cryptographic...Rule Medium Severity -
The DNS implementation must prohibit recursion on authoritative name servers.
A potential vulnerability of DNS is that an attacker can poison a name server's cache by sending queries that will cause the server to obtain host-to-IP address mappings from bogus name servers tha...Rule Medium Severity -
The DNS server implementation must authenticate another DNS server before establishing a remote and/or network connection using bidirectional authentication that is cryptographically based.
Without authenticating devices, unidentified or unknown devices may be introduced, thereby facilitating malicious activity. Bidirectional authentication provides stronger safeguards to validate the...Rule Medium Severity -
The DNS server implementation, for PKI-based authentication, must implement a local cache of revocation data to support path discovery and validation in case of the inability to access revocation information via the network.
Without configuring a local cache of revocation data, there is the potential to allow access to users who are no longer authorized (users with revoked certificates). SIG(0) is used for server-to-...Rule Medium Severity -
A DNS server implementation must provide data origin artifacts for internal name/address resolution queries.
The major threat associated with DNS forged responses or failures is the integrity of the DNS data returned in the response. The principle of DNSSEC is to mitigate this threat by providing data ori...Rule Medium Severity -
A DNS server implementation must provide data integrity protection artifacts for internal name/address resolution queries.
The major threat associated with DNS forged responses or failures is the integrity of the DNS data returned in the response. The principle of DNSSEC is to mitigate this threat by providing data ori...Rule Medium Severity -
A DNS server implementation must provide additional integrity artifacts along with the authoritative name resolution data the system returns in response to external name/address resolution queries.
The major threat associated with DNS forged responses or failures is the integrity of the DNS data returned in the response. The principle of DNSSEC is to mitigate this threat by providing data ori...Rule Medium Severity -
A DNS server implementation must request data origin authentication verification on the name/address resolution responses the system receives from authoritative sources.
If data origin authentication and data integrity verification are not performed, the resultant response could be forged, it may have come from a poisoned cache, the packets could have been intercep...Rule Medium Severity -
A DNS server implementation must request data integrity verification on the name/address resolution responses the system receives from authoritative sources.
If data origin authentication and data integrity verification are not performed, the resultant response could be forged, it may have come from a poisoned cache, the packets could have been intercep...Rule Medium Severity -
A DNS server implementation must perform data integrity verification on the name/address resolution responses the system receives from authoritative sources.
If data origin authentication and data integrity verification are not performed, the resultant response could be forged, it may have come from a poisoned cache, the packets could have been intercep...Rule Medium Severity -
A DNS server implementation must perform data origin verification authentication on the name/address resolution responses the system receives from authoritative sources.
If data origin authentication and data integrity verification are not performed, the resultant response could be forged, it may have come from a poisoned cache, the packets could have been intercep...Rule Medium Severity -
If the DNS server is using SIG(0), the DNS server implementation must only allow the use of DoD PKI-established certificate authorities for verification of the establishment of protected transactions.
Untrusted Certificate Authorities (CA) can issue certificates, but they may be issued by organizations or individuals that seek to compromise DoD systems or by organizations with insufficient secur...Rule Medium Severity -
The DNS server implementation must utilize cryptographic mechanisms to prevent unauthorized modification of DNS zone data.
Applications handling data requiring "data at rest" protections must employ cryptographic mechanisms to prevent unauthorized disclosure and modification of the information at rest. Selection of a ...Rule High Severity -
The DNS server implementation must utilize cryptographic mechanisms to prevent unauthorized disclosure of non-DNS data stored on the DNS server.
Applications handling data requiring "data-at-rest" protections must employ cryptographic mechanisms to prevent unauthorized disclosure and modification of the information at rest. Selection of a ...Rule High Severity -
The DNS server implementation must protect the integrity of transmitted information.
Without protection of the transmitted information, confidentiality and integrity may be compromised since unprotected communications can be intercepted and either read or altered. Communication p...Rule High Severity -
The DNS server implementation must implement cryptographic mechanisms to detect changes to information during transmission unless otherwise protected by alternative physical safeguards, such as, at a minimum, a Protected Distribution System (PDS).
Encrypting information for transmission protects information from unauthorized disclosure and modification. Cryptographic mechanisms implemented to protect information integrity include, for exampl...Rule Medium Severity -
The DNS server implementation must maintain the integrity of information during preparation for transmission.
Information can be either unintentionally or maliciously disclosed or modified during preparation for transmission, including, for example, during aggregation, at protocol transformation points, an...Rule Medium Severity -
The DNS server implementation must maintain the integrity of information during reception.
Information can be either unintentionally or maliciously disclosed or modified during reception, including, for example, during aggregation, at protocol transformation points, and during packing/un...Rule Medium Severity -
The DNS server implementation must behave in a predictable and documented manner that reflects organizational and system objectives when invalid inputs are received.
A common vulnerability of applications is unpredictable behavior when invalid inputs are received. This requirement guards against adverse or unintended system behavior caused by invalid inputs, wh...Rule Medium Severity -
The DNS server implementation must perform verification of the correct operation of security functions: upon system start-up and/or restart; upon command by a user with privileged access; and/or every 30 days.
Security function is defined as the hardware, software, and/or firmware of the information system responsible for enforcing the system security policy and supporting the isolation of code and data ...Rule Medium Severity -
The DNS implementation must generate audit records for the success and failure of start and stop of the name server service or daemon.
Auditing and logging are key components of any security architecture. It is essential for security personnel to know what is being performed on the system, where an event occurred, when an event oc...Rule Medium Severity -
The salt value for zones signed using NSEC3 RRs must be changed every time the zone is completely re-signed.
NSEC3 RRs contain other options than just the (hashed) next name and RRType bitmap. There are also 2 values associated with the NSEC3 RR: the iterations (number of times each name is hashed) and th...Rule Medium Severity -
The validity period for the RRSIGs covering a zones DNSKEY RRSet must be no less than two days and no more than one week.
The best way for a zone administrator to minimize the impact of a key compromise is by limiting the validity period of RRSIGs in the zone and in the parent zone. This strategy limits the time durin...Rule Medium Severity -
The DNS implementation must ensure each NS record in a zone file points to an active name server authoritative for the domain specified in that record.
Poorly constructed NS records pose a security risk because they create conditions under which an adversary might be able to provide the missing authoritative name services that are improperly speci...Rule Medium Severity -
All authoritative name servers for a zone must be located on different network segments.
Most enterprises have an authoritative primary server and a host of authoritative secondary name servers. It is essential that these authoritative name servers for an enterprise be located on diffe...Rule Medium Severity -
An authoritative name server must be configured to enable DNSSEC Resource Records.
The specification for a digital signature mechanism in the context of the DNS infrastructure is in IETF's DNSSEC standard. In DNSSEC, trust in the public key (for signature verification) of the so...Rule Medium Severity -
In a split DNS configuration, where separate name servers are used between the external and internal networks, the external name server must be configured to not be reachable from inside resolvers.
Instead of having the same set of authoritative name servers serve different types of clients, an enterprise could have two different sets of authoritative name servers. One set, called external ...Rule Medium Severity
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