Did you read the article? If not, I'll post the first paragraph again (and I'll alert you to the relevant passages using highlights):
Concern is growing at the top levels of government about the US-Mexican border becoming a back door for terrorists entering the United States. While Al Qaeda infiltration across the nation's southern border has been a constant concern since 9/11, US officials cite recent intelligence giving the most definitive evidence yet that terrorists are planning to use it as an entry point.
I read the article. Did you read my posts? I won't copy and paste them, I'll just let you read them again, if you prefer, and I'll even give you a little hint: do you think it would be easier to pick out a dozen terrorists from a million illegal border crossers or from a thousand?