[1] Alexander attended the United States Military Academy at West Point, and in his class were three other future four-star generals: David Petraeus, Martin Dempsey and Walter L. Sharp.

In April 1974,[dubious – discuss] Alexander married Deborah Lynn Douglas, who was a classmate in high school and who grew up near his family in Onondaga Hill.

In the words of James Bamford, who wrote his biography for Wired, "Alexander and the rest of the American intelligence community suffered a devastating defeat when they were surprised by the attacks on 9/11."

Testifying to the Senate Armed Services Committee, Alexander called the abuse "totally reprehensible" and described the perpetrators as a "group of undisciplined MP soldiers".

[13] In 2004, along with Alberto Gonzales and others in the George W. Bush administration, Alexander presented a memorandum that sought to justify the treatment of those who were deemed "unlawful enemy combatants".

[14] In June 2013, the National Security Agency was revealed by whistle-blower Edward Snowden to be secretly spying on the American people with FISA-approved surveillance programs, such as PRISM and XKeyscore.

[1] Also during this period, Alexander oversaw the implementation of the Real Time Regional Gateway in Iraq, an NSA data collection program that consisted of gathering all electronic communication, storing it, and then searching and otherwise analyzing it.

[17] This "collect it all" strategy introduced by Keith Alexander is believed by Glenn Greenwald of The Guardian to be the model for the comprehensive world-wide mass archiving of communications which NSA had become engaged in by 2013.

[18] According to Siobhan Gorman of The Wall Street Journal, a government official stated that Alexander offered to resign after the 2013 global surveillance disclosures first broke out in June 2013, but that the Obama administration asked him not to.

We can succeed in securing it by building strong partnerships between and within the private and public sectors, encouraging information sharing and collaboration, and creating and leveraging the technology that affords us the opportunity to secure cyberspace ...[22] Alexander gave the most comprehensive interview of his career, which spanned some 17,000 words, on 8 May 2014 to the Australian Financial Review journalist Christopher Joye, which was subsequently cited by Edward Snowden.

[23] The full transcript, which covers NSA operations, Snowden, the metadata debates, encryption controversies, and Chinese and Russian spying, has been published online.

[25][26] In July 2012, in response to a question from Jeff Moss, founder of the DEF CON hacker convention, "... does the NSA really keep a file on everyone?," Alexander replied, "No, we don't.

"[28] On 6 June 2013, the day after Snowden's revelations, then-Director of National Intelligence James Clapper released a statement admitting the NSA collects telephony metadata on millions of Americans telephone calls.

[31] Andy Greenberg of Forbes said that NSA officials, including Alexander, in the years 2012 and 2013 "publicly denied—often with carefully hedged words—participating in the kind of snooping on Americans that has since become nearly undeniable.

[37] In early October 2024 the AP reported that an investment bank had approached over 100 prospective buyers for the company, citing federal records, but none of them made an offer.