The failure to put Umar Farouk Abdulmutallab on the watch list last year renewed concerns that the government’s system to screen out potential terrorists was flawed. Even though Abdulmutallab’s father had told U.S. officials of his son’s radicalization in Yemen, government rules dictated that a single-source tip was insufficient to include a person’s name on the watch list.

Since then, senior counterterrorism officials say they have altered their criteria so that a single-source tip, as long as it is deemed credible, can lead to a name being placed on the watch list…

But civil liberties groups argue that the government’s new criteria, which went into effect over the summer, have made it even more likely that individuals who pose no threat will be swept up in the nation’s security apparatus, leading to potential violations of their privacy and making it difficult for them to travel.

“They are secret lists with no way for people to petition to get off or even to know if they’re on,” said Chris Calabrese, legislative counsel for the American Civil Liberties Union.