Thursday, July 30, 2009

BIND 9 Denial of Service Attacks in the Wild


Earlier today Marc posted a short diary about a vulnerability in the Internet Systems Consortium's BIND 9 (all versions). As you almost certainly know, BIND is the most popular DNS service application running on majority of DNS servers today – and DNS is one service that we *really* need.

As the DoS attacks have been seen in the wild, and simple scripts that can be used to reproduce the attack are also easily available, this is not really surprising.

I wanted to draw your attention to this vulnerability (if you are running a BIND DNS server) – although the vulnerability exists in the dynamic update feature of BIND, even installations that have dynamic updates disabled are affected! This makes this vulnerability especially dangerous.

Only servers hosting master zones are vulnerable though, so even if the master DNS servers are down, all slaves should still continue to work (I'm not sure what happens if those slaves are masters for some other zones and they are subsequently taken down).

No workarounds exist – you might be able to create some firewall rules that will drop these packets though. In any case, it is recommended to upgrade your BIND DNS servers urgently from

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