How do I stop someone from illegally sending messages from my yahoo email acct.?

(Sorry it's a long answer, but it's complicated question/solution.) This has been happening to both Yahoo and Hotmail accounts, but even more so recently. Weak passwords shorter than completely random 12+ characters are a big problem! Your address may have been found in someone else's infected computer's address book, and is being used by spammers. You may have opened an infected Spam mail or an attachment. Some new malware can install itself just by opening it, without even clicking a link! (It only takes a few hours to crack an 8-character password!) http://www.infopackets.com/news/security/2011/20110621_new_email_scams_stealthier_than_ever_report.htm If none of these mails show in your Sent folder, it is not your own computer that is infected. Check there first. Deleting your account will NOT stop this spam - once the spammers have the address, they will continue to use it for a while. 1. Check that the alternate e-mail address is still yours (Change it?), and then change both your password AND your secret questions and answers. Make them unique and 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 with Networking' is most effective) http://housecall.trendmicro.com/ http://www.malwarebytes.org/products/malwarebytes_free http://www.superantispyware.com/ 3. Then delete cookies, cache and history in case the malware can 'self- reproduce' ... http://www.piriform.com/ccleaner/download/standard Also, for individual browsers, see: http://www.wikihow.com/Clear-Your-Browser's-Cache http://www.wikihow.com/Clear-Your-Browser's-Cookies http://www.wikihow.com/Clear-Your-Online-Activity 4. 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 (alternate address) 5. If these spams/spoofs do not stop, you will need to set up a new account. https://edit.yahoo.com/registration?.int (new address)