DNS Tampering Prompts Homeland Security Warning

The US Department of Homeland Security's Cybersecurity and Infrastructure Security Agency (CISA) has issued an emergency directive that addresses ongoing incidents ascribed to global Domain Name System (DNS) infrastructure tampering.

Yes, in the middle of the self-inflicted shutdown the US government is freaking out.

The DNS hijacking effort has now been found to be affecting government domains. The summary page of the emergency directive uses links that refer to the hijackings -- attributed to Iran -- that have been previously reported by Talos and FireEye.

In a notice, CISA asserts that it is aware of multiple executive branch agency domains that were affected by the tampering campaign and has notified the agencies that maintain them. The agency describes the attack methodology it has encountered, which seems very similar to those which have been already described by the security companies.

(Source: iStock)

The attacker begins by compromising user credentials -- or obtaining them through alternate means -- of an account that can make changes to DNS records.

The attacker alters DNS records, such as Address (A), Mail Exchanger (MX), or Name Server (NS) records, replacing the legitimate address of a service with an address that the attacker controls. It can then pass the traffic on to the legitimate address. This threat lasts beyond the period of traffic redirection.

With the change in DNS records, the attacker can obtain valid encryption certificates for an organization's domain names. This allows the redirected traffic to be decrypted, exposing any user-submitted data. Since the certificate is valid for the domain, end users receive no error warnings.

The directive specifies certain steps that it directs affected agencies to take within the next ten business days from January 22:

• Audit DNS records associated with government domains to verify that they have not been tampered with and are directing traffic to the correct IP addresses.
• Change the passwords for DNS admin accounts that modify DNS records.
• Add multi-factor authentication (MFA) to all DNS admin accounts. It should be noted that the CISA has in the past advised against the use of SMS-based MFA.
• Begin to monitor the Certificate Transparency (CT) logs for agency domains that will be provided by DHS within the next ten business days.

These steps have no termination date associated with them, although they could be terminated by another directive.

Affected agencies will need to submit a status report by Friday, January 2, and a completion report that all of the actions have been completed by February 5.

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— Larry Loeb has written for many of the last century's major "dead tree" computer magazines, having been, among other things, a consulting editor for BYTE magazine and senior editor for the launch of WebWeek.