With any website that has important data, hackers are prone to attack it. If your Yahoo! Mail account was recently hacked or you received a phishing e-mail trying to get private information and sign-in credentials, you should immediately report the incident to the Yahoo! security team. You can report phishing attempts or hacked accounts from the Yahoo! Security Center.
Open a Web browser and type "security.yahoo.com" as the URL in the address field. Press the "Enter" key.
Go to the "Phishing" section and click "How do I report a phishing e-mail or web site?" link.
Go to the "Report a phishing e-mail" section and locate the "this form" link in the middle of the paragraph. Click the "this form" link to report hacking.
Click the "What is the violation?" drop-down menu and select "My account has been hacked."
Type your "Yahoo! ID" under the "Who are you reporting?" section. Fill in the other areas of the form as necessary. In the "Additional Information" text area, though it is optional, you should give a thorough explanation of the potential hacking threat or successful hacking attempt.
Fill in the "How may we contact you?" section with your name, Yahoo! ID and e-mail address. If you cannot access your Yahoo! Mail any longer, you should use an alternative e-mail. Click "Submit."