The wave of unrest sweeping the Middle East and North Africa is complicating the mission of American intelligence officials focused on tracking terrorists, the Wall Street Journal reports.

In countries like Libya, Yemen and elsewhere, popular uprisings have displaced government officials who have served as liaisons to U.S. intelligence. "It's difficult to share information when you don't know who the players are," an unnamed U.S. official told the newspaper.

In the process, the activities and whereabouts of some former Guantanamo Bay detainees now living in those countries have fallen through the cracks.

The group taking greatest advantage may be the Yemen-based al-Qaida in the Arabian Peninsula. The Journal cites U.S. and European officials saying they've seen an increase in activity, with one source saying that, in the absence of U.S. military strikes and Yemeni crackdowns, the group is "very actively" plotting attacks against the United States.

Similar vulnerabilities now exist in Tunisia, Egypt and Libya.