Security researchers from Symantec have identified 49 more modules of the sophisticated Regin cyberespionage platform that many believe is used by the U.S. National Security Agency and its close allies.

This brings the total number of modules known so far to 75, each of them responsible for implementing specific functionality and giving attackers a lot of flexibility in how they exploit individual targets.

Regin came to light in November last year, but it has been in use since at least 2008 and antivirus companies have known about it since 2013.

It is one of the most sophisticated malware threats discovered to date and has been used to target Internet service providers, telecommunications backbone operators, energy firms, airlines, government entities, research institutes and private individuals.

Most of the infections detected by Symantec were in Russia and Saudi Arabia, but compromised targets have also been found in Mexico, Ireland, India, Afghanistan, Iran, Belgium, Austria and Pakistan.

Regin has a modular architecture, which allows its creators to add or remove specific features to the malware program depending on their target and goal.

Some of the modules implement basic malware functions like command-and-control communications, taking screen shots, controlling the mouse, stealing passwords, capturing network traffic, gathering information about programs running on the infected computers, recovering deleted files and more.

Other modules are much more specialized and built with specific targets in mind. "One module was designed to monitor network traffic to Microsoft Internet Information Services (IIS) web servers, another was observed collecting administration traffic for mobile telephony base station controllers, while another was created specifically for parsing mail from Exchange databases," the Symantec researchers said in an updated version of their white paper published Thursday.

The malware also has a complex command-and-control infrastructure that uses peer-to-peer communications between infected computers, virtual private networking and six different transport protocols that are implemented as separate modules: ICMP, UDP, TCP, HTTP Cookies, SSL, and SMB.

Even though 75 Regin modules have been found so far, there are likely many more that have yet to be discovered.

"A number of other Regin payloads are known to exist since some modules analyzed contain references to them," the Symantec researchers said Thursday in a blog post.

There are strong indications that Regin is a unified computer network exploitation (CNE) platform codenamed WARRIORPRIDE that is used by the intelligence agencies of the U.S., U.K., Canada, Australia and New Zealand -- known as the Five Eyes intelligence partnership.

WARRIORPRIDE, also known as DAREDEVIL at the U.K. Government Communications Headquarters (GCHQ), was described in a secret document authored by the Communications Security Establishment Canada that was leaked by former NSA contractor Edward Snowden.

According to the document, the Five Eyes intelligence partners can create and share plug-ins for the platform. That would explain the very large number of Regin modules in existence.

In January, German news magazine Der Spiegel released a keylogger program dubbed QWERTY that it said was likely part of WARRIORPRIDE and was included in the trove of files leaked by Snowden. Researchers from antivirus firm Kaspersky Lab later concluded that QWERTY was identical to the Regin 50251 plugin and even had code referencing a different Regin module.

Despite the attack platform being exposed, it's unlikely that the group behind it will cease operations, the Symantec researchers said. "Its track record and available resources mean it is probable that the group will re-equip itself with a new threat or upgrade Regin in a bid to evade detection. The latter is the most likely course of action, given the time it would take to develop an equally capable malware framework from scratch."