You could look at putting in place a grunty server with
squid, dansguardian and the clam-av patch for dans-
guardian (which should get rid of the nasty's). Not sure
how much cheaper it's going to be since the grunt required
of the box heavily depends on the size and usage of the
network. Also note that (and that's not a flaw but a natural
consequence of the setup) web-virii and spyware that come
in via ssl connections won't be picked up by either concept,
and you'll still need tools on the desktops, too.


Cheers,
Tink