[Oisf-users] Hostbits?

Matt matt at somedamn.com
Wed Feb 6 20:42:27 UTC 2013

Is there a way to tag hosts rather than flows?  As a specific use case, 
there's a model of Netgear router that sometimes gets stuck in a loop 
flooding DNS requests.  I'd like to be able to distinguish those from 
other high volume DNS clients.  One way to pick out a Netgear router is 
DNS requests for time-a.netgear.com and time-b.netgear.com, but that's 
not always what they flood.  I'd like to be able to write something like 

# Set a hostbit with a 12 hour expiration
alert udp $HOME_NET any -> $DNS_SERVERS 53 (msg:"Netgear 
time-a.netgear.com"; content:"|06|time-a|07|netgear|03|com"; 
hostbits:set netgear, hours 12; hostbits:noalert)
alert udp $HOME_NET any -> $DNS_SERVERS 53 (msg:"Broken Netgear Flood"; 
hostbits:isset netgear; threshold:type both, track by_src, count 60000, 
seconds 600; classtype:denial-of-service;)

- Matt

More information about the Oisf-users mailing list