The word “free” is always dicey when you talk about computer software. Usually, free software is a loss-leader for the software company, and such software often comes bundled with stuff which tries to separate you from your money later on. And, in the worst cases, this “stuff” is spyware, which spies on you, trying to figure out how to sell you more stuff.
Nevertheless, there are some computer security companies which make available some good antivirus software, and they give it away to home users. Those companies hope to make money later, either from upgrades, or indirectly as a marketing cost leading to higher trust levels (for instance, tech people buy their software for non-home situations) I often will recommend these packages to my clients, and they work well in a pinch.
The biggest problem with these programs is that they can turn into “nagware” – that is to say, they start nagging you to buy an upgrade. AVG, for instance, used to be pretty quiet, but now (in 2008) its newest version is total nagware.
- Avast! 4, from the Czech company Alwil. http://avast.com/eng/download-avast-home.html The main annoyance with this software is the yearly registration requirement, but that is no more or less annoying than some website registrations.
- AVG Free, also from a Czech company, AVG (formerly Grisoft). http://free.avg.com/download-avg-anti-virus-free-edition — AVG has been amping up the upgrade nags quite a bit lately, so if you install this, be prepared.
- Comodo Internet Security: http://www.comodointernetsecurity.com/download_cis.html — This program is a bit technical and geeky, but its latest upgrade strikes me as worthwhile.
There are a few other currently free antivirus software packages – for instance, Avira AntiVir and Eeye Blink – but I can’t say anything one way or another on those two.