Someone is sending spam from my address book how can I stop it?

(Sorry it's a long answer, but it's complicated question/solution. I've done much reading and much research for it.) 1. Check that alternate e-mail address is still the same, and then change both your password AND your secret questions. Make them strong ones! 2. Run both an anti-virus and spyware/malware scan, separately - even more than one malware scan, or Trend Micro's Housecall for an online a-v scan. (in Safe Mode is best) http://www.malwarebytes.org/mbam.php http://housecall.trendmicro.com/ 3. Notify all your contacts NOT to open short e-mails, especially those with no subject, and definitely not to click any links. Warn them to scan for malware too, just in case. Set up an alternate 'alias' account to use instead. This allows you to use a different address but still keep all saved mails and contacts and the first address active too for incoming mail. http://edit.yahoo..com/config/list_alias%E2%80%A6 (alternate address) 4. If these spams/spoofs do not stop, you will need to set up a new account. https://edit.yahoo.com/registration?.int%E2%80%A6 (new address)

Your account got compromised. First change your password. Account help.http://help.yahoo.com/l/us/yahoo/acct/in%E2%80%A6 for just about anything to do with your account. Then run anti Virus and Anti Spyware. Should be fine then.