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DNS ANY Request Cannon - Need More Packets
We have a report from our reader Tuukka, who observed a flood of DNS ANY requests from likely spoofed IP addresses. What we know so far is that it seems to be a DNS Reflective Amplification Attack. These usually use generic recursive DNS queries trolling for poorly configured DNS services. This event is different in that the reflection is more targeted. DNS 'ANY' record queries are only sent for domains for which the server is authoritative for, which the server will of course reply to regardless of available recursion. These events have been validated by a real time observation by one of our handlers. Here is what we know so far.
Hit List:
- Source IP is spoofed
- Flood lasts up to 60 seconds with 500 queries (as witnessed, but likely could be more)
- Flood comes from a designated IP and seem to target multiple domains on authoritative server
- All observed requests are similar thus far
- This appears to be similar to what others have seen [1]
Example DNS Log Entry:
- x.x.x.x is the spoofed/target server
- example.com/10.1.1.1 is the "reflecting" DNS server
21-May-2012 13:21:41.757 queries: info: client x.x.x.x#20475: view external: query: example.com IN ANY + (10.1.1.1)
21-May-2012 13:21:41.897 queries: info: client x.x.x.x#59247: view external: query: example.com IN ANY + (10.1.1.1)
21-May-2012 13:21:42.054 queries: info: client x.x.x.x#18676: view external: query: example.com IN ANY + (10.1.1.1)
21-May-2012 13:21:42.059 queries: info: client x.x.x.x#28530: view external: query: example.com IN ANY + (10.1.1.1)
21-May-2012 13:21:42.193 queries: info: client x.x.x.x#6489: view external: query: example.com IN ANY + (10.1.1.1)
We are interested in knowing if you have seen this and what you have done to mitigate any ill effects of such events. Please post a comment to let us know.
We also want your DNS logs and packet capture logs of the events described in this diary. There is still plenty to learn about this behavior.
If you see outbound ANY query floods from your own network: Try to identify the source machine. It would be interesting to see what tool causes these queries.
-Kevin
--
ISC Handler on Duty
ISC StormCast for Monday, May 21st 2012 http://isc.sans.edu/podcastdetail.html?id=2548
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