You can sell a steam account with a bunch of games on it for quite a bit. What does it matter to the person that steals them if they're recovered after they've been sold? What the virus is probably doing is attempting to the steal the accounts, considering it's using Steam specifically to spread itself around.
The best advice I can give for protecting your steam account is to have at least one hard copy of a game that can be activated on Steam by serial key. I have a hard copy of HL2, and if my account is stolen I can send a photo of the back of the box with the serial key and a slip of paper with my account name on it. That's enough to prove your ownership to Valve. Obviously you should use a strong password and not share it with anyone either.
And don't click sketchy links.