The government is notifying some defendants accused of terrorism that it used more National Security Agency surveillance than it disclosed during their court proceedings.

The third such notification was made Monday to an Albanian citizen who pleaded guilty and is serving a 15-year prison sentence.

The notifications are a result of a Justice Department review of certain terror cases. It is unclear how many cases are affected or what the notifications could mean for defendants' abilities to challenge evidence or their convictions.

The secret surveillance at issue is the NSA's collection of communications of non-Americans living outside the U.S. Former NSA systems analyst Edward Snowden revealed details of this program when he disclosed classified documents last year. The president has called for a review of the surveillance.