In the realm of software firewalls ISA Server is the
most sophisticated available. Typically installed as a gateway to the rest
of your network the server allows for controlled publishing of in house web
sites, FTP and mail servers and VPN connections.
ISA has a
very large range of features (it takes MS
describe them); some examples: it allows for control or total blockage of a
specific computer form your LAN out to the web. You can prevent/monitor a
computer's access to internet messaging or any other protocol your workers
might be abusing.
Rather than re-write Microsoft's pages, I suggest you take a look
at their site, or give us a call