Snowden and others have contended that he did America and the world a service by revealing information on secret programs, which they say wrongly impinge on people's right to privacy in furtively giving too much information to the U.S. government.
But in his speech Thursday in Baltimore, the head of the National Security Agency argued -- as he's done repeatedly in recent weeks -- that the programs both protect civil liberties and help keep America and its allies safe.
Alexander pointed to 54 related cases that Congress was informed about, of which 50 led to arrests or detentions. Most of these were centered overseas, with 13 exceptions such as a foiled 2009 plot to bomb New York City's subway system. Exposing the programs, he and others have said, makes it harder to spot terrorists and thus puts lives at risk.
"I believe the irresponsible release of classified information about these programs will have a long-term detrimental impact on the intelligence community's ability to detect future attacks," Alexander said. "These leaks have inflamed and sensationalized, for ignoble purposes, the work that (the) intelligence community does lawfully, over strict oversight and compliance."
Possible Snowden posts
On Wednesday, the technology website Ars Technica published portions of chat logs it said show comments from 2009 by someone using a forum name Snowden was known to have used. The comments criticized people who leak national security information.
Commenting on New York Times reporting based on leaks related to confidential surveillance programs involving Iran, the poster compared the newspaper to WikiLeaks -- which enraged U.S. officials by disclosing thousands of confidential diplomatic cables.
"Are they TRYING to start a war?" the poster wrote. "you don't put that s*** in the NEWSPAPER."
Ars Techica said it could not be certain the poster was Snowden, but information revealed in the posts matches biographical information he has since publicly revealed. CNN could not verify the posts' authenticity .
If they were written by Snowden, they offer insight into his thinking at a time when he apparently was more accepting of government surveillance programs.
According to Ars Technica, the poster said of the New York Times and its reporting on secret surveillance programs, "these are the same people who blew the whole 'we could listen to osama's cell phone' thingthe same people who screwed us on wiretappingover and over and over againThank god they're going out of business."
Four years later, Snowden would provide news organizations in the United States and the United Kingdom with classified information he acknowledged copying and taking from his job as a computer contractor for the NSA in Hawaii.