A former National Security Agency analyst who was arguably its most damaging traitor and became famous for aiding the Soviets during the cold war died last week, according to an obituary posted on the website of a Maryland funeral home.

Ronald William Pelton was 80.

Pelton was an NSA intelligence communications specialist who, in November 1985, was arrested for selling government secrets to the Soviet Union. He spent about three decades in prison before he completed serving his sentence in 2015.

Pelton’s crimes included selling defense and communication secrets for upwards of $35,000. His most notable breach of trust was informing Soviet intelligence of “Operation Ivy Bells”, a plan put forward by the NSA and the US navy to tap the Soviets’ underwater communication cables.

He worked for the NSA for 14 years and retired in 1979, after which he approached the Soviet embassy in Washington to sell government secrets. Pelton’s lawyer said he had betrayed the US because he had fallen on hard financial times and was desperate.

At the time, Peloton was making $24,500 a year, which – accounting for inflation – is an estimated $100,000 today.

A Soviet KGB agent who had defected reported Pelton to investigators, setting the stage for his prosecution.

Despite asking for leniency, Pelton was given three life sentences, plus another 10 years to be served at the same time.

“I could at least make the rest of my life count,” Pelton pleaded. His pleas were denied.

He was freed from his sentence after stints at a halfway house and then under home confinement.

A federal judge said Pelton committed “one of the most serious offenses in the US criminal code”.

Pelton’s lawyer in the case, Fred Warren Bennett, called his client’s act of espionage “the biggest mistake of his life”.

On his obituary page, Pelton’s daughter Pamela Wright commented: “When I was 19, he left and didn’t return until I was nearly 50. During that span of time there was almost no communication. I grew up. Had a family. Went to college and gained a professional career. Had grandchildren. I lived my life without him.

“When he came back, he was quieter. More mellow. With many regrets.”