Squid in the Middle

Network- and host-based intrusion detection is pretty much a mandatory requirement now if you want to keep your network under control. Back in the good old days, when your Internet connection was a dial-up link (for the entire company), you could just keep software up to date, install a firewall, and call it a day.

Since then, things have changed significantly. Almost all computers are now attached to the Internet all the time. Most of these computers are behind firewalls and NAT-based systems – so they can use the Internet, but the Internet can’t initiate connections to them. This strategy worked pretty well until clients started using prodigious amounts of data from the Internet, especially the World Wide Web and email. Now, to add insult to injury, almost all web and email clients include JavaScript support and newer technologies like HTML5 and web sockets.