Google yesterday said it would again host its Pwnium hacking contest at a Canadian security conference in March, putting $2.7 million at stake to draw out researchers who can hack its browser-based operating system, Chrome OS. Dubbed Pwnium 4, the challenge will again pit researchers against Chrome OS, but this year will let them choose between Intel- or ARM-powered laptops. In 2013, hackers had to try to crack a Chromebook with an Intel processor.