I would like to ask for some assistance/validation on a signature issue I’m facing right now.
The Customer tried to create an App-ID to identify and block any snmp traffic that has the Community String value of ‘public’ or ‘private’, and block snmp probes with those string values (not traps).
The App-ID didn’t work for obvious reasons (no context for snmp), and trying to create a vulnerability signature will lead me to the same problem, not to mention the 7 bytes limitation for ‘public’ that is one byte short, I tried some other community names to test but no dice, I believe that the missing context is responsible for this issue, and to use the udp-unkown context would be wrong because the traffic is known as (snmp-base).
We did find an Snort signature offering the exact same thing:
alert udp $EXTERNAL_NET
any -> $HOME_NET 161 (msg:"SNMP public access udp"; content:"public"; reference:bugtraq,2112; reference:bugtraq,4088; reference:bugtraq,4089; reference:cve,1999-0517; reference:cve,2002-0012; reference:cve,2002-0013; classtype:attempted-recon; sid:1411; rev:10;)
But due to our limitations I couldn’t replicate the signature, maybe because I’m missing something and that’s why I would like to reach out to all of you.
Do we have a workaround for this?
Can we have a specific context for snmp created or some kind of contentless regex adoption?
What solutions could be offered (if any) at this moment?
I highly appreciate any assistance,
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