[Snort-sigs] lots of alerts on so rule "possible DGA detected"

kestutis.malakauskas at ...3980... kestutis.malakauskas at ...3980...
Tue Nov 25 04:52:39 EST 2014


Hello,

The same here we do see lots of (FP) hits. Doesn’t seem this SIG to be very useful at this point.

Kestutis

Kestutis Malakauskas |  Lead Attack Monitoring Analyst  | Global Information Security | Security Operations
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From: Ronny Vaningh [mailto:ronny at ...3979...]
Sent: 25 November 2014 09:56
To: snort-sigs at lists.sourceforge.net
Subject: [Snort-sigs] lots of alerts on so rule "possible DGA detected"

Hi

I'm seeing a lot of alerts on an SO rule that looks for DGA's.

alert udp $EXTERNAL_NET 53 -> $HOME_NET any (msg:"PROTOCOL-DNS domain not found containing random-looking hostname - possible DGA detected"; sid:31738; gid:3; rev:1; classtype:trojan-activity; metadata: engine shared, soid 3|31738, service dns;)


It seems to trigger on dns requests that are appending search domains like

First the host does a request for myserverhostname001.subdomain.domain.com<http://myserverhostname001.subdomain.domain.com>
After receiving a NXDOMAIN it appends a search domain suffix and generates a request like

myserverhostname543.subdomain.domain.com.searchdomain.com<http://myserverhostname543.subdomain.domain.com.searchdomain.com>



Does anyone knows what this SO rule is actually looking for and is there any way I can influence this, since it looks pretty useful so I want to avoid disabling it.


Regards


Ronny


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