Loose-knit hacking groups like Anonymous and LulzSec hacked numerous Web sites in 2011 and stole massive amounts of data -- some of which ended up being published on the Web, USA Today reported Tuesday.
Groups involved in the politically motivated attacks have been comparing notes, experts say.
"They are learning from each other," Kris Harms, principal consultant of network security firm Mandiant, said. "Corporations and governments need to recognize (more) break-ins are inevitable."
The new wave of ideological hacking began a little more than a year ago when Anonymous temporarily crippled the Web sites of Visa, MasterCard, PayPal and others in retaliation for those companies refusing to process payments from WikiLeaks.
A recent highest-profile hack was Anonymous' breach of Strategic Forecasting's Web site, in which so-called hacktivists publicly posted credit card records for tens of thousands of the online publication's subscribers, along with their e-mail addresses, phone numbers and encrypted passwords.
By posting stolen information as proof of an attack, hacktivists are making such data readily accessible to ID thieves, Identity Finder Chief Executive Officer Todd Feinman said.
"Collateral damage to average consumers has become a very big problem," he said.