#11 Yahoo's massive breach

Yahoo apologized in July for a network breach that compromised users’ data. About 400,000 Yahoo user names and passwords, among other information were exposed. The breach was especially bad because it tied in with Gmail, Hotmail and other online accounts. The hacker group who claimed the responsibility said it used a SQL injection.

Yahoo's apologized over this issue: “At Yahoo! we take security very seriously and invest heavily in protective measures to ensure the security of our users and their data across all our products. We confirm that an older file from Yahoo! Contributor Network containing approximately 400,000 Yahoo! and other company users’ names and passwords was stolen yesterday, July 11. Of these, less than 5 percent of the Yahoo! accounts had valid passwords. We are fixing the vulnerability that led to the disclosure of this data, changing the passwords of the affected Yahoo! users and notifying the companies whose users’ accounts may have been compromised. We apologize to affected users. We encourage users to change their passwords on a regular basis and also familiarize themselves with our online safety tips at security.yahoo.com."