Along with his alleged computer-hacking activities, Tanenbaum is suspected of teaching others how to enter the systems.
The investigation began in the summer of 1997, when U.S. officials launched a probe into a series of break-ins at the NASA computers.
Early last year, there were additional break-ins, which prompted a further inquiry involving the U.S. Army, Navy and Justice Department.
The probe by U.S. investigators led to two Sonoma County youths, who confessed to breaking into several computer systems.
They also said they had learned how to break-in to the computers from an Israeli who called himself “The Analyzer.” A search of their homes turned up information that helped investigators discover Tanenbaum’s identity.
In March, FBI agents came to Israel to request the cooperation of local authorities in arresting Tanenbaum.