[Snort-sigs] Asprox sig

James Lay jlay at ...3266...
Tue Jul 9 16:33:26 EDT 2013


On 2013-07-09 14:23, lists at ...3397... wrote:
> On 07/09/2013 03:15 PM, James Lay wrote:
>> alert tcp $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS
>> (msg:"msg:"MALWARE-CNC Asprox outbound connection";
>> flow:to_server,established; content:"?v="; http_uri; content:"&id=";
>> http_uri; within:6; content:"&b="; http_uri; content:"&tm="; 
>> http_uri;
>> within:7; metadata:impact_flag red, policy balanced-ips drop, policy
>> security-ips drop, service http;
>> 
>> reference:url,http://labs.m86security.com/2010/06/the-asprox-spambot-resurrects/;
>> classtype:trojan-activity; sid:10000085; rev:1;)
>
> I recommend we had some negations to avoid some falses, for example,
> the lack of
> proper headers is pretty bogus.  Header ordering is pretty important
> too, so I'd
> probably do this:
>
> content:"|20|HTTP/1.1|0d 0a|User-Agent|3a 20|"; fast_pattern:only;
> content!:"Accept"; http_header; {the rest of your content matches for
> HTTP URI}
>
> Good stuff James, as always.
>
> Cheers,
> Nathan

Thanks Nathan,

Here's the mod:

alert tcp $HOME_NET any -> $EXTERNAL_NET $HTTP_PORTS 
(msg:"msg:"MALWARE-CNC Asprox outbound connection"; 
flow:to_server,established; content:"|20|HTTP/1.1|0d 0a|User-Agent|3a 
20|"; fast_pattern:only; content!:"Accept"; http_header; content:"?v="; 
http_uri; content:"&id="; http_uri; within:6; content:"&b="; http_uri; 
content:"&tm="; http_uri; within:7; metadata:impact_flag red, policy 
balanced-ips drop, policy security-ips drop, service http; 
reference:url,http://labs.m86security.com/2010/06/the-asprox-spambot-resurrects/; 
classtype:trojan-activity; sid:10000085; rev:2;)

Running this now in production.

James




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