A former sys admin at Medco Health Solutions, a US prescription management and health information firm, has been jailed for 30 months over a failed attempt to destroy its systems using a "logic bomb" computer virus.

Yung-Hsun Lin, 51, of Montville, New Jersey, was sentenced this week after earlier pleading guilty to booby-trapping systems at Medco.

Yung-Hsun had feared he might lose his job after the firm's spin-off from Merck, and set the 'bomb' to go off after his expected departure.

The malware, planted in October 2003, was designed to wipe out critical data stored on more than 70 servers. The data included a patient-specific drug interaction conflict database as well as billing and payroll systems.

When the code failed to launch in April 2004 because of coding flaws, Yung-Hsun (who survived a round of lay-offs) reprogrammed the malware to go off on April 23, 2005 - his next birthday. Fortunately the malware was discovered and defused in January 2005 before it could do any damage, after a sys admin investigating a system error discovered the malware embedded within other scripts on Medco’s servers. ®

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