Scanning LAN for virus activity?

[Michael St. Laurent]

I was reading about the String module for iptables in Linux Journal over the
weekend and it occured to me that this could be used for scanning the LAN
for the presence of an infected system.

Does anyone know if such a tool exists?  We're seeing *much* higher network
activity lately than in the past and it makes me nervous.

--
Michael St. Laurent
Hartwell Corporation