(CNN) —  

Thirteen alleged members of the cyberhacking group “Anonymous” have been indicted by a federal grand jury in suburban Washington, accused of targeting governmental entities, trade associations, individuals, law firms, and financial institutions starting in 2010.

In a 28-page document, the defendants are charged in an Alexandria, Virginia, federal court with conspiracy. Prosecutors say they “planned and executed a coordinated series of cyber-attacks against victim websites by flooding those websites with a huge volume of irrelevant Internet traffic with the intent to make the resources on the websites unavailable to customers and users of those websites.”

The alleged cyberhacking campaign was purportedly dubbed “Operation Payback.”