McAfee's lawyer, Javier Villapa, said the antivirus software pioneer hanged himself in frustration after 9 months in prison.
Last month, McAfee, 75, said during a hearing that by the time he reached that age, he would spend the rest of his life in prison if convicted in the United States.
Despite being a pioneer in the field of computer security, McAfee previously admitted to the BBC that he had not used his software or any other security software on the computers he owned.
In an interview with the BBC's Leo Killion in 2013, McAfee said, "I always protect myself by constantly changing the IP address, not entering my name on any device I use, and not visiting websites that may be a source of the virus," and added, "Like porn site.
"I hope the Spanish Supreme Court will see the extent of this injustice," he said. "The United States wants to make me an example to others."
McAfee fled the US authorities for years, some of which he spent on a huge yacht. He was charged in Tennessee with tax evasion and cryptocurrency fraud in New York.
A Spanish police source said at the time that McAfee had been detained on October 3 at Barcelona airport, as he was about to board a plane to Istanbul with a British passport.
McAfee worked for NASA, Xerox and Lockheed Martin, before launching the world's first commercial anti-virus program in 1987.
Did John McAfee commit suicide, or was he murdered in a Spanish prison? John McAfee was a rebel, a software pioneer, and a wanted criminal in the United States. While John McAfee was alive, he said many times if he was found dead by suicide that it would be a lie, even going as far to tattoo the word "$Whackd" on his right arm ...at one point John McAfee compared his impending death to that of Jeffrey Epstein, who was found dead in his jail cell in New York City, Epstein was ruled to have killed himself, though many claim it was murder. What do you believe?
He sold his software company to Intel in 2011 and is no longer involved in the business. The program still bears his name and has 500 million users around the world.
It is noteworthy that sources indicated that his wealth at the time of his death amounted to only 4 million dollars, after it was more than 100 million dollars 15 years ago.
