"In a Shadowserver six-month test between June and December 2011, ClamAV detected over 75.45% of all viruses tested, putting it in fifth place behind AhnLab, Avira, BitDefender and Avast. AhnLab, the top antivirus, detected 80.28%.[9]"
> Can it intercept network traffic
"On Linux servers ClamAV can be run in daemon mode, servicing requests to scan files sent from other processes. These can include mail exchange programs, files on Samba shares, or packets of data passing through a proxy server (IPCop, for example, has an add-on called Copfilter which scans incoming packets for malicious data)."
It seems that there is a third party tool that provides heuristic detection.
