Malwarebytes' free Anti-Malware software actually has a 4.5 star rating from CNET editors and users (5,145 votes) and is a legitimate anti-virus program. Make sure to update your virus definition files frequently because this popular (and very good) program is often targeted by malware to keep you from staying on top of the latest bad apples.
Lavasoft's Ad-Aware is free and gets updated frequently as well. We like to run both Ad-Aware and Anti-Malware one after the other - what one misses the other catches it seems. It doesn't hurt and they're both free. Ad-Aware does have a tendency to kill your cookies, but it doesn't hurt to eat fewer cookies. Full scans can take hours though, so be patient or run scans overnight.
The successor to Microsoft's wishy-washy Defender software, it's free for Windows owners and from the big boys who wrote your PC's operating system. You'd think they'd have a good idea of their own OS's weaknesses, right? We leave this running on our own systems, downloading updates and performing a full scan every night.
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