Symantec documents a highly advanced form of spyware that is very stealth-like and difficult to detect and may have been used in variety of attacks

http://www.symantec.com/connect/blogs/regin-top-tier-espionage-tool-enables-stealthy-surveillance

http://www.symantec.com/content/en/us/enterprise/media/security_response/whitepapers/regin-analysis.pdf

http://www.symantec.com/security_response/writeup.jsp?docid=2013-121221-3645-99

 

An advanced piece of malware, known as Regin, has been used in systematic spying campaigns against a range of international targets since at least 2008. A back door-type Trojan, Regin is a complex piece of malware whose structure displays a degree of technical competence rarely seen. Customizable with an extensive range of capabilities depending on the target, it provides its controllers with a powerful framework for mass surveillance and has been used in spying operations against government organizations, infrastructure operators, businesses, researchers, and private individuals.