The feds revealed Tuesday they're putting new scrutiny on immigrants who overstay visas.
Agents are running overstayed-visa files through multiple security, immigration and law enforcement databases, a top Homeland Security official said.
They are automatically checking for national security risks, said John Cohen, the department's principal deputy coordinator for counterterrorism.
In the past, officials had to manually check each one.
Cohen said at a congressional hearing on visa security that the new system is "a pretty fully baked approach to how we're going to deal with this issue."
Homeland Security has been under pressure to update visa screening since its creation - after four of the 9/11 hijackers were in the country on out-of-date or invalid visas.
Although the Obama administration said this summer that Immigration and Customs Enforcement should prioritize deportations - and allow noncriminals and those with family ties to the U.S. to stay - all overstayed visas will be vetted for security concerns, regardless of priority, Cohen said.
Before the department began automatically screening the visas this spring, a backlog of 1.6 million unchecked overstays mounted.
After running automated checks, they found that 800,000 had either fixed their visa status or left the country, Cohen said.
They then went through the 839,000 that were left and flagged 2,000 that warranted investigation for national security or public safety reasons, Cohen said.
Many of those were either already in jail or out of the country, but Cohen said that by July, Immigration and Customs Enforcement agents were pursuing a dozen new leads.
In their review of the visa program, the 9/11 Commission also recommended setting up a biometric exit program that would "log out" immigrants here on visas when they leave the country.
This was never fully put in place, and Homeland Security officials have said it would be too expensive.