DarkFiber Consulting – IT Managed Services

NAT/PAT Affects DNS Cache Poisoning Mitigation

July 23rd, 2008 . by DarkFiber Consulting

DarkFiber Consulting released a Current Activity entry and a Vulnerability Note on July 8, 2008 regarding deficiencies in DNS implementations. These deficiencies could leave an affected system vulnerable to cache poisoning. Technical details regarding this vulnerability have been posted to public websites. Attackers could use these details to construct exploit code. Users are encouraged to patch systems or apply workarounds immediately.

A number of patches implement source port randomization in the name server as a way to reduce the practicality of cache poisoning attacks. Administrators should be aware that in infrastructures where nameservers exist behind Network Address Translation (NAT) and Port Address Translation (PAT) devices, port randomization in the nameserver may be overwritten by the NAT/PAT device and a sequential port address could be allocated. This may weaken the protection offered by source port randomization in the nameserver.

DarkFiber Consulting encourages users to consider one of the following workarounds:

  • Place the nameserver outside of the NAT/PAT device in the network infrastructure.
  • Configure the NAT/PAT device to perform source port randomization.
  • Configure the NAT/PAT device to preserve the source port assigned by the nameserver.

Additional information can be found in DarkFiber Consulting Vulnerability Note VU#800113.

More information will be provided as it becomes available.

DNS Implementations Vulnerable to Cache Poisoning

July 14th, 2008 . by DarkFiber Consulting

DarkFiber Consulting is aware of deficiencies in the DNS protocol. Implementations of this protocol may leave the affected system vulnerable to DNS cache poisoning attacks. If an attacker can successfully conduct a cache poisoning attack, they may be able to cause a nameserver’s clients to contact the incorrect, and possibly malicious, hosts for particular services. This may allow an attacker to obtain sensitive information or mislead users into believing they are visiting a legitimate website.

DarkFiber Consulting encourages users to review “VU#800113 – Multiple DNS implementations vulnerable to cache poisoning” and apply any necessary solutions listed in that document to help mitigate the risks.

DarkFiber Consulting will provide additional information as it becomes available.