You can get your hands on free anti-virus software — but even when there’s no upfront cost, unreliable virus protection can become expensive.

To help IT decide what’s worth the price, PCWorld recently rated popular, no-cost anti-virus programs. The top three:

1. Avira AntiVir Personal – Reportedly fast with excellent protection, featuring a 98.9% overall malware detection rate. Two supposed problems, though: a confusing interface and annoying daily pop-up ads.
2. Alwil Avast Antivirus – Testers say it has solid protection features and quick scanning. However, the outdated interface could use some improvements. The app blocked 98.2% of the malware samples in a test.
3. AVG 8.5 Free – It’s easy to use, with useful Web attack blocking, testers said, but its malware detection couldn’t hold up to Avira and Alwil.