While one focus of the leak crackdown announced on Friday by US Attorney General Jeff Sessions is on journalists who receive leaked information, another is on suspected leakers.
Republican President Donald Trump has complained for months about leaks to the news media, but his Democratic predecessor, Barack Obama, also took a hard line on leaking.
Eight of the 12 cases where federal prosecutors charged individuals with violating the Espionage Act, a World War One-era law aimed at keeping sensitive information out of the hands of the United States' enemies, were brought under Obama. Here are the 12 cases, dating back 46 years.
Daniel Ellsberg became the first such case in 1971 when prosecutors accused the national security analyst and his colleague, Anthony Russo, of providing what would become known as the Pentagon Papers to the New York Times and other media outlets. The secret documents revealed the extent of US involvement in Vietnam. Charges against the two men were dismissed when a judge found that the government had wiretapped Ellsberg, possibly illegally.
Samuel Morison, a former Navy intelligence analyst, was charged in 1984 with illegally passing secret photographs of Soviet ships to a magazine, Jane's Defence Weekly. He pleaded not guilty, but a jury convicted him, making him the first person convicted under the Espionage Act for divulging secrets to the press. He was sentenced to two years in prison but paroled. President Bill Clinton pardoned him.
Lawrence Franklin, a Defence Department employee, was charged in 2005 with passing classified information about Iran to two pro-Israel lobbyists, Steven Rosen and Keith Weissman. Franklin pleaded guilty and received a 12-year sentence. Eventually, after the government's case against Rosen and Weissman collapsed, a judge reduced Franklin's sentence to 10 months in a halfway house.
Shamai Leibowitz was an FBI translator when material that he heard while translating ended up on a blog. He reached an agreement with prosecutors before he was charged, and pleaded guilty in 2009 to one count of disclosing classified information. He was sentenced to 20 months in prison.
Former National Security Agency official Thomas Drake was suspected in 2010 of revealing information about the agency's warrantless wiretapping program. He was indicted under the Espionage Act but said the only information he leaked was about waste in an NSA program, which he gave to the Baltimore Sun. The 10 felony counts were dropped when he pleaded guilty to a misdemeanor and received no prison time.
Chelsea Manning, an Army private first class formerly known as Bradley Manning, turned over more than 700,000 classified files to the anti-secrecy website WikiLeaks in the biggest breach of secret data in US history. Manning was found guilty of 19 counts but acquitted of the most serious one, aiding the enemy. She was sentenced in August 2013 to 35 years in a military prison but was released in May after Obama, in his last days in office, commuted the final 28 years of Manning's sentence.
Stephen Kim, a US State Department contract analyst, allegedly divulged to a Fox News reporter what US intelligence believed about how North Korea would respond to new sanctions. A grand jury indicted him in 2010 for disclosing defence information and making false statements. He pleaded guilty in 2014 and was sentenced to thirteen months in prison. He was released in May 2015.
Former CIA officer Jeffrey Sterling was charged in 2011 with illegally disclosing classified information about Iran to James Risen, a New York Times reporter, for his book "State of War." A jury convicted Sterling in 2015. A judge sentenced him to 42 months in prison.
Former CIA officer John Kiriakou was charged in 2012 with divulging to journalists secret information about the CIA's interrogation program, including the identity of a covert officer. In an agreement with prosecutors, he pleaded guilty to one count and was sentenced to two and a half years in prison. He was released in February 2015 on condition that he serve three months of house arrest.
US officials said in June 2013 they had filed sealed criminal charges against former NSA contractor Edward Snowden for unauthorized leaks and theft of government property. Snowden prompted a worldwide debate after he gave documents to newspapers showing the extent of US surveillance programs. Russia granted him asylum.
Former FBI bomb analyst Donald Sachtleben agreed in September 2013 to plead guilty to disclosing national defence information for telling an Associated Press reporter details of a failed airline bombing attempt by Yemen-based al-Qaeda in the Arabian Peninsula. A judge sentenced Sachtleben that year to a 43-month prison term for the national security offences and a consecutive 97-month term for unrelated child pornography charges.
The Justice Department charged US intelligence contractor Reality Leigh Winner with violating the Espionage Act for leaking a classified report on Russian interference in US elections to The Intercept. The NSA report described Russian efforts to launch cyber attacks on at least one US voting software supplier and send "spear-phishing" emails to more than 100 local officials days before the November 8, 2016 election.