51 terror suspects nabbed trying to enter U.S. illegally

WorldNetDaily is reporting that since tracking began fourteen months ago, At least 51 people who crossed the border illegally have been arrested on suspicion of terrorism.
My question is: If we caught 51 people, how many got in without being detected?
With our porous boarders, it's only a matter of time before we get another terrorist attack, probably much worse then the one we experienced on 9-11.

At least 51 people who crossed the border illegally have been arrested on suspicion of terrorism since such tracking began 14 months ago, according to figures released to Rep. Tom Tancredo, R-Colo., by the Department of Homeland Security.
Tancredo, a leading congressional advocate of immigration reform, says the figures document the national security risk the nation's porous borders pose on the eve of Congress' first attempt in nearly a decade to rewrite immigration law.
Since October 2004, the Joint Terrorism Task Forces have kept track of arrested terrorist suspects who are in the U.S. illegally.
The JTTF document released to Tancredo shows 51 people were arrested who had "entered without inspection" into the U.S. from countries such as Iran, Iraq, Lebanon, Egypt, Syria and Pakistan.
"If this isn't a wake-up call to our lax border security, I don't know what is," said Tancredo. "What scares me is not this list from federal law enforcement – after all, we've already caught those terrorists. What scares me is the potentially hundreds of terrorists who make their way through our porous borders each year and go undetected."
The suspected illegal alien terrorists were arrested on a wide variety of charges, from smuggling weapons to illegally wiring large sums of money into the country, the document says.

Read the rest here.