The desktop Web browser has long been a security sinkhole. It's grown deeper, despite emphasis on secure coding, greater user awareness, improvements to Internet Explorer and the use of alternatives like Firefox and Opera. Criminals lure users to thousands of malicious or compromised Web sites to scam their identity information or drop some nasty code on their computers.

Detecting these sites and collecting and countering exploits has been somewhat like playing Whack-A-Mole, but security...