Last week, a computer virus attacked the State Department’s electronic system known as CLASS, the Consular Lookout and Support System. The system, which contains records from the FBI, State Department and U.S. immigration, drug-enforcement and intelligence agencies, and is used to check visa applicants for terrorist or criminal history, failed worldwide, making the U.S. government unable to issue visas.

The State Department’s automated systems are programmed to not print a visa until the visa applicant is checked against the names in the CLASS database. Included in the database’s 12.8 million records are the names of 78,000 suspected terrorists.

An internal message was circulated among embassies and consulates warning that CLASS was “down due to a virus found in the system.” While it is unclear which specific virus attacked the system, a separate message sent to embassies and consular offices warned that the “Welchia” virus had been detected in one facility.

Welchia exploits a software flaw in recent versions of Microsoft Windows. This virus, and the related “Blaster” virus have infected hundreds of thousands of government computers worldwide, including those at the Federal Reserve in Atlanta, Maryland’s motor vehicle agency and the Minnesota Transportation Department.

The CLASS system, which had no backup system available immediately, was shut down for several hours. An embassy spokesman in Seoul said that it was a “short outage” and that visa interviews continued to take place.