Free antivirus

[Antonio Alberto Lobato <tomlobato@ig.com.br>]

	Hi all,

	After a search on google and mailing lists archives, doubts remains...

	Is there available a free and good antivirus for run on GNU/Linux (but searching windows viruses)?
	My needs is to protect a network of 90 windows machines where the GNU/Linux is the gateway/firewall/proxy-cache/ftp/pop3/smtp server (A duron 1300MHz). So, Id like to have hints about where to install this antivirus: filtering proxy-cache traffic, or scanning the pop3/smtp server, or both?
	The pop3/smtp servers here are just for internal mail exchange, so users continue to sending/retrieving mail to/from external mailboxes such yahoo, hotmail. Is it possible to scan viruses for such external mailboxes? 
	If there is not a good free solution, can you give hints about good options for proprietary ones?



	Thank you
	Tom