Which former FBI agent was convicted of espionage?

The conviction of Robert Hanssen for espionage is significant because he was one of the most damaging spies in U.S. history. Hanssen, who worked as an FBI agent, was arrested in 2001 and later pleaded guilty to selling secrets to the Soviet Union and later to Russia over a period of more than 20 years. His actions compromised numerous investigations and placed lives at risk, as he provided sensitive information related to American intelligence operations, the names of sources, and counterintelligence measures. His case serves as a critical example of espionage from within a trusted position in the government, highlighting the potential threats posed by insider threats in counterintelligence.