U.S. intelligence and law enforcement investigators have concluded that they might never know the entirety of what the former National Security Agency contractor
Investigators remain in the dark about the extent of the data breach partly because the NSA facility in
Six months since the investigation began, officials said, Snowden had further covered his tracks by logging into classified systems using the passwords of other security agency employees, as well as by hacking firewalls installed to limit access to certain parts of the system.
"They've spent hundreds and hundreds of man-hours trying to reconstruct everything he has gotten, and they still don't know all of what he took," a senior administration official said. "I know that seems crazy, but everything with this is crazy."
That Snowden was so expertly able to exploit blind spots in the systems of America's most secretive spy agency illustrates how far computer security still lagged years after President
Snowden's disclosures set off a national debate about the expansion of the NSA's powers to spy both at home and abroad, and have left the Obama administration trying frantically to mend relations with allies after his revelations about U.S. eavesdropping on foreign leaders.
A presidential advisory committee that has been examining the security agency's operations submitted its report to Obama on Friday. The
Snowden gave his cache of documents to a small group of journalists, and some from that group have shared documents with several news organizations - leading to a flurry of exposures about spying on friendly governments. In an interview in October, Snowden said he had given all of the documents he downloaded to journalists and kept no additional copies.
In recent days, a senior NSA official has told reporters that he believes Snowden still has access to documents not yet disclosed. The official,
"So, my personal view is, yes, it's worth having a conversation about," Ledgett told
Snowden is living and working in
Snowden has said he would return to
With the security agency trying to revamp its computer network in the aftermath of what could turn out to be the largest breach of classified information in U.S. history, the
According to senior government officials,
But for all of Snowden's technical expertise, some U.S. officials also place blame on the security agency for being slow to install software that can detect unusual computer activity carried out by the agency's workforce - which, at approximately 35,000 employees, is the largest of any intelligence agency.
An NSA spokeswoman declined to comment.
Former NSA contractor