Reporting illegal aliens falls under the authority of ICE (Immigration and Customs Enforcement) and reporting employers of illegal aliens falls under the authority of the IRS.
Department of Homeland Security:
"Investigative and enforcement responsibilities for enforcement of federal immigration laws, customs laws, and air security laws was transferred to the U.S. Immigration and Customs Enforcement (ICE)."
http://www.dhs.gov/dhspublic/theme_home4.jsp
Remain anonymous, and report illegals, for the safety of our Borders... the thing I think people fail to see is that Al Queida (not sure of the spelling, but you get the drift) or other enemies of the USA can get into our country and hurt or attempt to hurt innocent civilians... if they see a Mexican immigrant can do it, what's to prevent them, from filtering in amongst the Mexicans? I love all people, and don't think anyone should be kept out of our great nation, as long as he/she follows the rules... they aren't perfect, but they're the rules. Our laws aren't perfect, but I believe we've got the best system in the world! Nothing in this world is perfect, but one of the reasons many nations hate the USA is envy!
We aren't bad people for wanting our nation secure, and we aren't evil for wanting to make an example of illegal aliens, who come here by breaking the law... what a way to start out!; being a criminal! Not agreeing with the law, is not an excuse for not obeying the law, right? So, for all you protesters out there; Piss Off!
I hope you aren't going to report anyone, just to make life difficult, but if you've got a legitimate beef with someone being illegal; (and someone with two names is fishy, and even worse, two SSN's? nope, I hate liars, no matter their intentions!), you can report them to ICE, or a local Federal building, or anonymously through websites such as:
http://www.reportillegals.com/ (for real!) But I'd go to the feds!
I also believe in Karma, so what goes around, comes around... don't bring negatives on yourself man, but do do the right thing.
I hope this helped!;
Peace!