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Re: How should ISPs notify customers about Bots (Was Re: DNS Hijacking

  • From: Roland Dobbins
  • Date: Tue Jul 24 13:40:42 2007
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On Jul 24, 2007, at 8:59 AM, Joe Greco wrote:

But, hey, it can be done, and with an amount of effort that isn't substantially different from the
amount of work Cox would have had to do to accomplish what they did.

Actually, it's requires a bit more planning and effort, especially if one gets into sinkholing and then reinjecting, which necessitates breaking out of the /32 routing loop post-analysis/-proxy. It can and is done, but performing DNS poisoning with an irchoneyd setup is quite a bit easier. And in terms of the amount of traffic headed towards the IRC servers in question - the miscreants DDoS one another's C&C servers all the time, so it pays to be careful what one sinkholes, backhauls, and re-injects not only in terms of current traffic, but likely traffic.

In large networks, scale is also a barrier to deployment. Leveraging DNS can provide a pretty large footprint over the entire topology for less effort, IMHO.

Also, it appears (I've no firsthand knowledge of this, only the same public discussions everyone else has seen) that the goal wasn't just to classify possibly-botted hosts, but to issue self-destruct commands for several bot variations which support this functionality.

[Note: This is not intended as commentary as to whether or not the DNS poisoning in question was a Good or Bad Idea, just on the delta of effort and other operational considerations of DNS poisoning vs. sinkholing/re-injection.]

Public reports that both Cox and Time-Warner performed this activity nearly simultaneously; was it a coordinated effort? Was this a one- time, short-term measure to try and de-bot some hosts? Does anyone have any insight as to whether this exercise has resulted in less undesirable activity on the networks in question?

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Roland Dobbins <[email protected]> // 408.527.6376 voice

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