[Don Joe]

You don't know the half of it. The hosts file is searched BEFORE DNS, so a bad guy could easily insert an entry like www.paypal.com or www.ebay.com in your hosts file, which then sends you to an alternate "bad guy" site, and you could unknowingly enter your username and password.

Lock it.

Look at the "Locking the HOSTS File" section on this page at mvps.org, and download the two batch files to lock and unlock your hosts file. (You can just do it manually via command line, but the batch files make it easier.)

Blocking Unwanted Parasites with a Hosts File</a

[Don Joe]

PS: the mvps.org site has a nice ready-to-roll HOSTS file you can download.

You can read about it (and download it) from here: http://mvps.org/winhelp2002/hosts.htm

Or, if you just want to grab it straightaway (and already know where it goes), it's here: http://mvps.org/winhelp2002/hosts.txt