A Yahoo logo is pictured in front of a building in Rolle, 30 km (19 miles) east of Geneva, in this file picture taken December 12, 2012. Yahoo! Inc is shifting its main European tax base to Ireland from Switzerland, a Reuters examination of company statements and accounts shows, as pressure mounts on the Alpine nation to abolish some corporate tax incentives. Picture taken December 12, 2012.       REUTERS/Denis Balibouse (SWITZERLAND - Tags: BUSINESS POLITICS LOGO) - RTX18CHS

Yahoo ads spread CryptoWall ransomware

Getting malware on your computer can be devastating, but at least it's usually easy to avoid — unless, of course, popular sites are spreading it via legitimate advertisements.