Symantec researchers have identified a particularly sophisticated piece of malware, called "Regin" that was likely developed by a nation state and has been used to spy on governments, infrastructure operators, businesses, researchers and individuals since at least 2008.

"Regin displays a degree of technical competence rarely seen," Symantec said in a statement Sunday, released along with a technical white paper about the malware. Indications are that Regin "is one of the main cyberespionage tools used by a nation state."

Researchers have identified its use in 10 countries, mainly Russia and Saudi Arabia, as well as Mexico, Ireland, India, Afghanistan, Iran, Belgium, Austria and Pakistan.

Regin is a back-door-type Trojan, "customizable with an extensive range of capabilities depending on the target," Symantec said, adding that "it provides its controllers with a powerful framework for mass surveillance." Its development probably took months "if not years" and "its authors have gone to great lengths to cover its tracks."

Its first incarnation was used to spy on a number of organizations from 2008 to 2011 when it was "abruptly withdrawn," with a new version showing up last year, Symantec said.