Jason Cornish, 37, formerly an IT staffer at the U.S. subsidiary of Japanese drug-maker Shionogi, pleaded guilty Tuesday to computer intrusion charges in connection with the attack on Feb. 3, 2011. He wiped out 15 VMware host systems that were running e-mail, order tracking, financial and other services for the Florham Park, New Jersey, company.

"The Feb. 3 attack effectively froze Shionogi's operations for a number of days, leaving company employees unable to ship product, to cut checks, or even to communicate via e-mail," the U.S. Department of Justice said in court filings. Total cost to Shionogi: US$800,000.

Cornish had resigned from the company in July 2010 after getting into a dispute with management, but he had been kept on as a consultant for two more months.

Then, in September 2010, the drug-maker laid off Cornish and other employees, but it did a bad job of revoking passwords to the network. One employee, who was Cornish's friend and former boss, allegedly refused to hand over network passwords to company officials and eventually was fired because of this.

Using a Shionogi account, Cornish was able to log into the company's network from a public McDonald's Internet connection in February and fire up a vSphere VMware management console that he'd secretly installed on the company's network a few weeks earlier.