Authorities in Switzerland have warned U.S. intelligence officials that a senior IT technician working for a Swiss intelligence service may have compromised U.S. and British counter-terrorism operations.

In September, Swiss attorney general Michael Lauber and a senior prosecutor, Carolo Bulletti, held a press conference to disclose the alleged data theft, and said that they had a suspect in custody. "The intention was to sell the data to other countries," said Bulletti, but authorities didn't know whether that had happened.

Earlier this week, Reuters reported that unnamed European intelligence sources with knowledge of the investigation said that Swiss authorities still haven't ascertained whether the suspect sold the data. That led Swiss authorities to warn all intelligence agencies that share counter-terrorism information with Switzerland -- including the CIA and Britain's Secret Intelligence Service, or MI6 -- that the information may have been sold to foreign intelligence agencies or commercial buyers.

[ The downfall of CIA director David Patraeus has lawmakers focusing on email and online privacy protection. Read more at The Petraeus Affair: Surveillance State Stopper? ]

The suspect worked for the NDB, Switzerland's federal intelligence service, which is part of its defense ministry, for eight years. He reportedly had administrator-level rights to most of the spy agency's networks, including ones storing highly secret information, and became disgruntled after feeling that higher-level managers were ignoring his recommendations.

Reportedly, the quantity of breached data involves terabytes of secret information and was stolen when the suspect copied it onto a portable hard drive and walked out of government premises with the drive stored in a backpack. Swiss authorities arrested the suspect -- who under Swiss laws can't be named -- in May, and said they recovered numerous portable devices containing the surreptitiously copied intelligence data. Authorities were tipped off by Swiss bank UBS, which had traced an attempt to open a new, numbered bank account to the IT technician. The suspect has been released on bail while the related investigation continues.

According to the European intelligence sources, the employee began displaying some of the classic warning signs that precede insider attacks, such as manifesting a disgruntled attitude and regularly failing to show up for work. The signs, however, were apparently ignored.

The Swiss case is far from the first time that a disgruntled IT-savvy employee with access to sensitive information has been accused of stealing it. In 2009, for example, MI6 caught Daniel Houghton, one of its computer programmers, trying to sell cutting-edge email interception technology, as well as staff lists containing cell phone numbers and home addresses for MI6 and Britain's MI5 domestic intelligence service. Houghton had downloaded at least 7,000 files onto a secure digital memory card and offered it for sale to the Dutch intelligence service, or AIVD. Dutch officials tipped off MI6, who busted Houghton in a sting operation.

Arguably, that data breach could have been prevented if proper controls been in place to monitor for unusual network behavior, such as copying 7,000 files to a removable memory card. The same, of course, could be said for the NDB in Switzerland, or for that matter, the Department of Defense, which saw 251,000 sensitive diplomatic cables get leaked to WikiLeaks. The alleged perpetrator, Private First Class Bradley Manning, an intelligence analyst, allegedly copied the data onto rewritable CDs, which he stored in a Lady Gaga CD case. According to psychologists, Manning's superiors ignored obvious insider-attack warning signs indicated in his emotional and mental state.

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