December 28. Tsutomu spends several days with Andrew and several other members of the Supercomputer Center staff poring over the faint traces left behind by the attackers.
After working virtually around the clock for several days, the small team is able to piece together the method of the attack. The intruder or intruders have taken advantage of the Internet's basic protocols by spoofing one of Tsutomu's computers, fooling it into believing that messages were being sent from a trusted source.
By understanding the attack, Tsutomu is able to improve his defenses, and he reattaches his computers to the Internet.
December 30. A second threatening voice mail message is left. The intruders have discovered that Tsutomu has strengthened his system's security and they promise that his "security technique will be defeated."