Kevin Poe was indicted in Los Angeles on two counts: conspiracy and unauthorized impairment of a protected computer. Poe made his initial appearance in court in Hartford, Conn., and was released on $10,000 bond.
If convicted of both charges, the Manchester man faces up to 15 years in prison. An email message left for deputy federal public defender Deirdre Murray was not immediately returned.
Poe and others linked to the Anonymous hacking group conducted a "denial of service" attack over a five-day period last October against Simmons' computer systems, sending tens of thousands of electronic requests designed to overload the server and render www.GeneSimmons.com useless.
Poe used a computer program favored by Anonymous that sends extremely large requests over a network in an attempt to overwhelm a target computer, according to the indictment.
Authorities didn't say why Simmons was targeted, but he made comments against copyright infringement at a convention in Cannes, France, days before the cyber attack.
No other arrests have been made.
Anonymous' targets have included MasterCard, Visa and the Church of Scientology. The group has turned its focus to law enforcement, intelligence and military-related sites.
Representatives for Simmons declined comment. The 62-year-old rocker was at a courthouse Tuesday for jury duty, according to his Twitter account.