An advanced spying tool, Regin displays a degree of technical competence rarely seen and has been used in spying operations against governments, infrastructure operators, businesses, researchers, and private individuals.

It is likely that its development took months, if not years, to complete and its authors have gone to great lengths to cover its tracks. Its capabilities and the level of resources behind Regin indicate that it is one of the main cyberespionage tools used by a nation state.


Microsoft identified Trojan:WinNT/Regin.A in 2011.


Someone submitted one of the malware sample to VirusTotal early in 2008.

Backdoor.Regin is a multi-staged threat and each stage is hidden and encrypted, with the exception of the first stage.  Executing the first stage starts a domino chain of decryption and loading of each subsequent stage for a total of five stages.  Each individual stage provides little information on the complete package. Only by acquiring all five stages is it possible to analyze and understand the threat.

Figure 1. Regin’s five stages

Regin also uses a modular approach, allowing it to load custom features tailored to the target. This modular approach has been seen in other sophisticated malware families such as Flamer and Weevil (The Mask), while the multi-stage loading architecture is similar to that seen in the Duqu/Stuxnet family of threats.

Timeline and target profile
Regin infections have been observed in a variety of organizations between 2008 and 2011, after which  it was abruptly withdrawn. A new version of the malware resurfaced from 2013 onwards. Targets include private companies, government entities and research institutes. Almost half of all infections  targeted private individuals and small businesses. Attacks on telecoms companies appear to be designed to gain access to calls being routed through their infrastructure.

Figure 2. Confirmed Regin infections by sector

Infections are also geographically diverse, having been identified in mainly in ten different countries.


Figure 3. Confirmed Regin Infections by country

Infection vector and payloads
The infection vector varies among targets and no reproducible vector had been found at the time of writing. Symantec believes that some targets may be tricked into visiting spoofed versions of well-known websites and the threat may be installed through a Web browser or by exploiting an application. On one computer, log files showed that Regin originated from Yahoo! Instant Messenger through an unconfirmed exploit.

Regin uses a modular approach, giving flexibility to the threat operators as they can load custom features tailored to individual targets when required. Some custom payloads are very advanced and exhibit a high degree of expertise in specialist sectors, further evidence of the level of resources available to Regin’s authors.

There are dozens of Regin payloads. The threat’s standard capabilities include several Remote Access Trojan (RAT) features, such as capturing screenshots, taking control of the mouse’s point-and-click functions, stealing passwords, monitoring network traffic, and recovering deleted files.

More specific and advanced payload modules were also discovered, such as a Microsoft IIS web server traffic monitor and a traffic sniffer of the administration of mobile telephone base station controllers.

Regin’s developers put considerable effort into making it highly inconspicuous. Its low key nature means it can potentially be used in espionage campaigns lasting several years. Even when its presence is detected, it is very difficult to ascertain what it is doing. Symantec was only able to analyze the payloads after it decrypted sample files.

It has several “stealth” features. These include anti-forensics capabilities, a custom-built encrypted virtual file system (EVFS), and alternative encryption in the form of a variant of RC5, which isn’t commonly used. Regin uses multiple sophisticated means to covertly communicate with the attacker including via ICMP/ping, embedding commands in HTTP cookies, and custom TCP and UDP protocols.

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. Its design makes it highly suited for persistent, long term surveillance operations against targets.

The discovery of Regin highlights how significant investments continue to be made into the development of tools for use in intelligence gathering.

Further reading
Symantec – Regin: Top-tier espionage tool enables stealthy surveillance

Kaspersky – Regin: Nation-state ownage of GSM networks