What is causing my computer to email my contact list?

Every month or so my computer emails all my contacts with an ad. I've run a virus scan [Avast] and malware scan [Malwarebyte's], but no luck. How do I get rid of this?

Anonymous2012-06-12T12:05:12Z

Favorite Answer

Your account got compromised. First change your password. Account help.http://help.yahoo.com/l/us/yahoo/acct/in… for just about anything to do with your account. Then run anti Virus and Anti Spyware. Should be fine then.

mmacpherson52012-06-12T14:41:29Z

Make sure you know every person who emails you.
If you get an e-mail addressed only to you and no one else. contact that person b4 opening the e-mail
Once a month sounds like you click on a link from *someone* you know and it copies your address book

Joe2012-06-12T13:02:31Z

Change your password and your security questions with your e-mail provider.

Some spammer has hacked them.