Clam AntiVirus (ClamAV), is a widely used free antivirus software toolkit for Unix-like operating systems. It is mainly used with a mail exchange server as a server-side email virus scanner. ClamAV is open source software distributed under the terms of the GNU General Public License (GPL). Both ClamAV and its updates are made available free of charge. ClamAV is generally configured to automatically update its list of virus definitions via the Internet (see : http://www.clamav.net).