Related: INS is the root cause of the flood of illegal immigrants in this country. Here's proof,
Law enforcement of these people has also proven to be a challenge. Back in early 2001 Mohammad Atta was pulled over for speeding and could not produce a license. It was later believed that he had an Egyptian license but either did not produce it or did not have it with him. He was told by the officer who pulled him over that a required court date was setup and if he did not attend a warrant would be out for his arrest. In the meantime Atta applied for, and received, a USA license and never attended the court date. A warrant was issued for his arrest. He was again pulled over for speeding and produced the USA license. A check on this license did not allow the officer to see that there was a warrant for Atta's arrest.
What went wrong here goes on more likely then we know and futute attacks can only be prevented if we start profiling.