9.1.2. IP Reputation Rules¶
IP Reputation can be used in rules through a new rule directive “iprep”.
The iprep directive matches on the IP reputation information for a host.
iprep:<side to check>,<category>,<operator>,<reputation score>
side to check: <any|src|dst|both>
category: the category short name
operator: <, >, =
reputation score: 1-127
alert ip $HOME_NET any -> any any (msg:"IPREP internal host talking to CnC server"; flow:to_server; iprep:dst,CnC,>,30; sid:1; rev:1;)
This rule will alert when a system in $HOME_NET acts as a client while communicating with any IP in the CnC category that has a reputation score set to greater than 30.
The “iprep” keyword is compatible to “IP-only” rules. This means that a rule like:
alert ip any any -> any any (msg:"IPREP High Value CnC"; iprep:src,CnC,>,100; sid:1; rev:1;)
will only be checked once per flow-direction.