Whether you block internet ads or not, Adblock Plus is a pretty handy Firefox extension. Not only can you use it to block offensive material, rickrolls and other unpleasant things, but Lifehacker reader Dave Farquhar lets us know that it also blocks malicious software.
Ads on the web can be all kinds of annoying, but some people prefer not to block every internet ad they see — after all, it is how most websites (including us here at Lifehacker) make their money and are able to keep pumping out content for free. Even if you don't block ads, though, it may be worthwhile to install Adblock Plus for Firefox, if not only for its malware-blocking powers.
You won't see it on the list of ad filters when you first install the Adblock extension, but a few folks have created a filter that maintains a listing of domains used for spreading spyware and malware. It started out as a tool for DNS servers, but has since been converted to a filter so those using Firefox could take advantage. Hit the link to read about it and subscribe to it, and don't forget to install Adblock Plus first if you haven't already.