Hacker groups that attack or steal -- some estimates say there are as many as 6,000 of such groups online with about 50,000 "bad actors" around the world drifting in and out of them -- are a threat, but the goals, methods, and effectiveness of these groups vary widely.
When they're angry, they hack into business and government systems to steal confidential data in order to expose information about their targets, or they simply disrupt them with denial-of-service attacks. These are the hackers with a cause, the "hacktivists" like the shadowy but well-publicized Anonymous or the short-lived Lulz Security group (which claimed to have just six members and just joined forces with Anonymous).
[ Also on InfoWorld: Anonymous eyes political role, but won't go legit. | Learn how to greatly reduce the threat of malicious attacks with InfoWorld's Insider Threat Deep Dive PDF special report. | Stay up to date on the latest security developments with InfoWorld's Security Central newsletter. ]
Malicious activity alert: Anonymous hack-school grads come online in 30 days
Over the years, Anonymous is believed to have hit targets that include the Church of Scientology, the Support Online Hip Hop website, the No Cussing Club website, and posted pornographic videos disguised as children's videos onto YouTube. It's said to have joined with Iranians protesting the results of the June 2009 Iranian presidential election. It's tied to taking down the Australian prime minister's website in 2009 because of the government's plans there to have ISPs censor porn on the Internet. Anonymous has taken up the cause of piracy activists fighting copyright law by launching denial-of-service attacks against anti-piracy groups and law firms. The group is supporting WikiLeaks, which publishes confidential information, including the U.S. State Department cables allegedly leaked by U.S. Army soldier Bradley Manning, now in a military jail awaiting trial.
Anonymous, perhaps tied to the Sony hacking incidents, has launched distributed DoS attacks against Amazon, PayPal, MasterCard, Visa and others when the card-payment groups refused to process donations to WikiLeaks. Anonymous has sprung into conflicts, such as this year's uprisings in the Mideast, hitting the websites of the Tunisian, Egyptian and Libyan governments. The group recently let the world know its chief focus these days is going to be targeting governments and corporations.
But hacktivists like Anonymous are just one type of hacker group. Others are out for financial gain, well-organized to steal payment-card numbers and personal financial data, or pillage bank accounts. And there are groups that focus on intellectual-property theft or steal valuable information for national interests, or money, or both.
Here's a look at what's known about some of them -- including the ones that unlike the hacktivists, seldom "Tweet" the world about what they do.