Drew Fitzgerald – WSJ.com – “Earlier this month, Brett Wentworth took Level 3 Communications Inc. into territory that most rivals have been reluctant to enter. The director of global security at the largest carrier of Internet traffic cut off data from reaching a group of servers in China that his company believed was involved in an active hacking attack. The decision was reached after a broad internal review. The Broomfield, Colo., company is taking an aggressive—and some say risky approach—to battling criminal activity. Risky because hackers often hijack legitimate machines to do their dirty work, raising the risk of collateral damage by sidelining a business using the same group of servers. Such tactics also run against a widely held belief that large carriers should be facilitating traffic, not halting it. And carriers are reluctant to create the expectation that they will police the Internet. Yet with attacks on the rise, Level 3 three years ago decided it is worth the risks. At a rate of about once every few weeks, the carrier is shutting down questionable traffic that doesn’t involve any of its clients. When the source of the trouble is hard to pinpoint, it often casts a wide net and intercepts traffic from large blocks of Internet addresses. Recently, that meant stopping traffic from a powerful network of computer servers controlled by a group of hackers that security researchers dubbed SSHPsychos. The group used rented machines in a data center to hack other computers that could bring down target websites by flooding them with junk traffic. Level 3 blocked a broad swath of the Hong Kong-registered data center’s IP addresses from the Internet.”