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Its first incarnation was used to spy on a number of organizations from 2008 to 2011 when it was "abruptly withdrawn," with a new version showing up last year, Symantec said. Nearly half of the Regin infections that have been identified involve private individuals and small businesses, with attacks on the telecommunication sector apparently aimed at gaining access to calls routed through that infrastructure.

The malware is a multistaged threat, with each stage hidden and encrypted, except for the first stage, execution of which initiates a domino decryption chain and loads each subsequent stage. There are five stages in total, with each offering scant information about the entire malware package, Symantec said. "Only by acquiring all five stages is it possible to analyze and understand the threat."

Regin also takes a modular approach, so that custom features of it are specific to its targets -- an approach used with other advanced malware families, inlcuding Flamer and Weevil. The multistage loading aspect of Regin is also akin to Duqu/Stuxnet malware, the researchers said. It is likely that its development took months, if not years.

Researchers have identified dozens of payloads, with some specific and advanced payload modules found, including a Microsoft IIS Web server traffic monitor and a traffic sniffer aimed at mobile telephone base-station controllers.

"Regin is a highly complex threat which has been used in systematic data collection or intelligence gathering campaigns. The development and operation of this malware would have required a significant investment of time and resources, indicating that a nation state is responsible," Symantec said. "Its design makes it highly suited for persistent, long-term surveillance operations against targets."

Symantec further believes that "many components of Regin remain undiscovered and additional functionality and versions may exist." Researchers are continuing their analysis and will provide public updates as additional discoveries about the malware are made, the company said.