[Snort-sigs] BOTNET-CNC Possible host infection - excessive DNS queries for .eu

Joel Esler jesler at ...435...
Mon Mar 12 11:18:20 EDT 2012


Which is why more specific signatures are written for this malware, and
this rule is disabled by default and in no policies.

On Mon, Mar 12, 2012 at 11:14 AM, Martin Holste <mcholste at ...2420...> wrote:

> The sig, as written, will false like crazy on any medium or large
> sized network because it does not take into account DNS servers or
> SMTP servers (or spam gateways) which do a lot of DNS lookups.
>
> On Mon, Mar 12, 2012 at 9:41 AM, Alex Kirk <akirk at ...435...> wrote:
> > First, you need the ".eu" bit because you need to have a content match in
> > the rule, else performance will suffer massively. Second, and more
> > important, the behavior we've seen centers around this particular TLD
> (and a
> > couple of others for which we have rules); we're targeting there to keep
> > false positives down.
> >
> > As far as this picking up other malware - chances are high it will. The
> rule
> > of thumb is to take a look at the domain names in the alerts, and
> determine
> > whether they're legitimate or not (which is usually obvious because
> > malicious ones are randomized), and then track back to the boxes
> generating
> > the queries for a thorough scan/investigation.
> >
> > On Sun, Mar 11, 2012 at 8:00 AM, Yew Chuan Ong <yewchuan88 at ...2420...>
> wrote:
> >>
> >> Hi,
> >>
> >> alert udp $HOME_NET any -> $EXTERNAL_NET 53 (msg:"BOTNET-CNC Possible
> host
> >> infection - excessive DNS queries for .eu"; flow:to_server;
> >> byte_test:1,!&,0xF8,2; content:"|02|eu|00|"; fast_pattern:only;
> >> detection_filter:track by_src, count 100, seconds 10;
> >> classtype:trojan-activity; sid:21544; rev:1;)
> >>
> >> This is the new sig posted on VRT blog recently which aimed to find out
> >> malware within the network. I am wondering why we need to specific on
> the
> >> keyword ".eu". Can we tracked the related traffic by using only the
> >> threshold?
> >>
> >> Also, are we aiming on any specific malware besides Murofet and Kazy? I
> >> try to google around but can't really get it. Thanks!
> >>
> >>
> >>
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> >
> >
> >
> >
> > --
> > Alex Kirk
> > AEGIS Program Lead
> > Sourcefire Vulnerability Research Team
> > +1-410-423-1937
> > alex.kirk at ...435...
> >
> >
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-- 
Joel Esler
Senior Research Engineer, VRT
OpenSource Community Manager
Sourcefire
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