Much like the day laborers they track, activists in Lake Forest, Calif., start their day before 7 a.m.
Armed with cameras, they try to shame employers who pick up illegal immigrants into stopping by posting the employers' photographs on the Web site WeHireAliens.com. They greet employers with signs saying, "Hiring a day laborer? Say cheese!"
Far from the theoretical debates on Capitol Hill, WeHireAliens.com is just one of many loosely affiliated citizens groups working against illegal immigration across the country.
The group congregates at day laborer sites from Herndon, Va., to Lake Forest, Calif., south of Los Angeles.
One employer in a pickup truck with two laborers called the group's tactics harassment.
"These folks have a right to make a living," he told ABC News.
As of Monday, the group had posted 843 employers from coast to coast on its site. They range from major corporations to small-business owners. But the group acknowledged it cannot prove that all day laborers are in the country illegally.
"It's not a perfect system," said Jason Mrochek of WeHireAliens.com. "Just like it's not a perfect system that we have all these illegal aliens running around and no one's doing anything about it."
But one day laborer, Pablo Garcia, said he has the proper papers. "I didn't do anything wrong to anybody," Garcia said. "The people need us and we offer. We are here for work."
The group said it's tough to judge how effective its efforts are. Employers complain about the activists being on the site, but certainly the hiring has not stopped -- nor has the tide of illegal immigration.
ABC News' Jake Tapper reported this story for "World News Tonight."