To my surprise, Windows Defender on Windows 8 Pro just popped up while I was looking in a shared folder that resides on my XP Pro computer.
It detected dll.dll and suckme files that I had put there (they are proof of concept and not harmful but good for testing a new AV). It said it was "cleaning" them. I was impressed that it detected "malware" on network shares. No other AV for consumer use does that (even Avast you would get it only if you purchased the Pro version and Avira has it only if you purchase Enterprise version and same for most others) that I am aware of.
It wasn't able to clean them...encountered an error because they are on a shared folder. It said it quarantined them but again it did not...the detailed info on each one said to remove them immediately.
I am impressed that it could detect malware on the network.--
When governments fear people, there is liberty. When the people fear the government, there is tyranny. Thomas Jefferson