Transparent Anti spam and virus web/mail/ftp Proxying on a Bridge

[T'Krin <tkrin () tkrin net>]

Hello everyone.

I am interested in setting up a bridge to check all web, mail and ftp
traffic for viruses and spam.  Setting up the bridge is the easy part, but
I'm wondering if any of you all could give recommendations on what proxy
applications may be useful.

I am planning on using ClamAV for the virus checking, and will use either
SpamAssassin or Dspam as well for spam.  DansGuardian looked valid as did
PCScan for web and pop3 proxying, but would appreciate any ideas you all
could share.

Thanks all.

~Dan