From the SquidClamav homepage:

SquidClamav is an antivirus for Squid proxy based on the Awards winnings
ClamAv anti-virus toolkit. Using it will help you securing your home or
enterprise network web traffic. SquidClamav is the most efficient Squid
Redirector and ICAP service antivirus tool for HTTP traffic available for
free, it is written in C and can handle thousand of connections. The way
to add more securing on your network for free is here.

SquidClamav is build for speed and security in mind, it is first used
and tested to secure a network with 2,500 and more users. It is also known
to working fast with 15000+ users. 

With SquidClamav You have full control of what kind of HTTP stream must be
scanned by Clamav antivirus, this control operate at 3 different levels:

- At URL level, you can disable virus scanning for a set of web site,
  filename extension or anything that can be matched in an URL.
- At client side by disabling virus scan and other redirector call
  to a set of username, source Ip addresses or computer DNS name.
- At HTTP header level, where you can disable virus scanning following
  the content type or file size.

WWW: http://squidclamav.darold.net