Snowden tricked NSA workers
It is not clear what rules the employees broke by giving Snowden their passwords.
Former US National Security Agency contractor Edward Snowden used login credentials and passwords provided unwittingly by colleagues at a spy base in Hawaii to access some of the classified material he leaked to the media, sources said.
A handful of agency employees, who gave their login details to Snowden were identified, questioned and removed from their assignments, said a source close to several US government investigations into the damage caused by the leaks.
Snowden may have persuaded between 20 and 25 fellow workers at the NSA regional operations center to give him their logins and passwords by telling them they were needed for him to do his job as a computer systems administrator, a second source said.
The revelation is the latest to indicate that inadequate security measures at the NSA played a significant role in the worst breach of classified data in the super-secret eavesdropping agency's 61-year history.
It is not clear what rules the employees broke by giving Snowden their passwords, which allowed the contractor access to data that he was not authorised to see.
Snowden worked at the Hawaii site for about a month last spring, during which he got access to and downloaded tens of thousands of secret NSA documents.
"In the classified world, there is a sharp distinction between insiders and outsiders. If you've been cleared and especially if you've been polygraphed, you're an insider and you are presumed to be trustworthy," said Steven Aftergood, a secrecy expert with the Federation of American Scientists.
Officials with the NSA and the Office of Director of National Intelligence declined to comment due to a criminal investigation related to Snowden, who disclosed previously secret US government mass surveillance programmes while in Hong Kong in June and then fled to Russia where he was granted temporary asylum.
People familiar with efforts to assess the damage to US intelligence caused by Snowden's leaks have said assessments are proceeding slowly because Snowden succeeded in obscuring some electronic traces of how he accessed NSA records.
The sources did not know if the NSA employees who were removed from their assignments were given other duties or fired.
While the US government now believes it has a good idea of all the data to which Snowden could have accessed, investigators are not positive which and how much of that data Snowden actually downloaded, the sources said.