At least a dozen US National Security Agency employees have been caught using secret government surveillance tools to spy on the e-mails or phone calls of their current or former spouses and lovers in the past decade, according to the intelligence agency's internal watchdog.
The practice is known in intelligence-world shorthand as "LOVEINT" and was disclosed by the NSA Office of the Inspector General in response to a request by the Senate Judiciary Committee's top Republican, Charles Grassley, for a report on abuses of the NSA's surveillance authority.
In one instance in 2005, a military member of the NSA queried six e-mail addresses of a former American girlfriend - on the first day he obtained access to the data-collection system.
He later testified that "he wanted to practise on the system" and gained no information.
In another instance, a foreign woman who was employed by the US government suspected that her lover, an NSA civilian employee, was listening to her phone calls. She shared her suspicion with another government employee, who reported it.
An investigation found the man abused NSA databases from 1998 to 2003 to snoop on nine phone numbers of foreign women and twice collected communications of an American.
The NSA's spying operations have come under intense scrutiny since disclosures this spring by former NSA contractor Edward Snowden that the US government collects far more internet and telephone data than previously publicly known.
Jameel Jaffer, deputy legal director at the American Civil Liberties Union, said the reported incidents of NSA employees' violations were likely "the tip of the iceberg" of lax data safeguards, but that the laws guiding the NSA's spying authority in the first place were a bigger issue.
"If you only focus on instances in which the NSA violated those laws, you're missing the forest for the trees," he said. "The bigger concern is not with wilful violations of the law but rather with what the law itself allows."