AP via SiliconValley.com, reports:

WASHINGTON (AP) - The State Department’s electronic system for checking every visa applicant for terrorist or criminal history failed worldwide late Tuesday because of a computer virus, leaving the U.S. government unable to issue visas.

The virus crippled the department’s Consular Lookout and Support System, known as CLASS, which contains more than 12.8 million records from the FBI, State Department and U.S. immigration, drug-enforcement and intelligence agencies. Among the names are those of at least 78,000 suspected terrorists.

In an internal message sent late Tuesday to embassies and consular offices worldwide, officials cautioned that “CLASS is down due to a virus found in the system.'’ There was no backup system immediately available, and officials could not predict how long the outage might last.

Such an outage would represent the most serious disruption in years to U.S. government computers from an Internet infection.

State Department spokeswoman Joanne Moore said the agency experienced some computer problems but could not confirm the visa-checking system was affected.

“We did have some computer problems,'’ she said. “They’re working on it.'’

Every visa applicant is checked against the names in the CLASS database. The State Department’s automated systems are designed not even to print a visa until such a check is completed.

It was unclear which computer virus might have affected the system. But a separate message sent to embassies and consular offices late Tuesday warned that the “Welchia'’ virus had been detected in one facility. Welchia is an aggressive infection unleashed last month that exploits a software flaw in recent versions of Microsoft Corp.’s Windows software.

Collectively, Welchia and a related virus, “Blaster,'’ have infected hundreds of thousands of computers worldwide, including computers at the Federal Reserve in Atlanta, Maryland’s motor vehicle agency and the Minnesota Transportation Department.

The State Department has invested heavily in the CLASS system since the Sept. 11, 2001, terror attacks, more than doubling the number of names that applicants are checked against. One provision of the Patriot Act, passed just weeks after the attacks, added FBI records, including the bureau’s violent gang and terrorist database. The list also includes the names of at least 20,000 people accused of serious Customs violations and the names of 78,000 suspected terrorists.