Hackers believed to be working for Western intelligence agencies breached the systems of Russian tech giant Yandex last year as part of an attack that involved a new variant of the Regin malware, Reuters reported on Thursday.

Reuters learned from four sources that the breach occurred between October and November 2018, it targeted Yandex’s research and development unit, and its goal was apparently to steal technical information on the company’s user authentication system. This information may have allowed the attackers to impersonate users and obtain their private messages.

While Reuters’ sources said the attackers had access to Yandex’s network for weeks before being detected, the Russian company’s representatives stated that the attack “was detected at a very early stage” and it was “fully neutralized before any damage was done.” The company also claimed no user data was compromised.

The attack was said to involve a new version of Regin, a stealthy attack platform that has been used to target organizations across various sectors and countries since at least 2008.

Discovered by Symantec in 2014, Regin was immediately believed to be the work of a state-sponsored threat actor and some have linked it to US and British intelligence. The malware was reportedly used in attacks targeting EU government networks and in an attack allegedly launched by the UK’s GCHQ intelligence agency against Belgian telecoms firm Belgacom.

Nearly half of the victims identified in the initial report on Regin were located in Russia and Saudi Arabia.

A later analysis by Symantec revealed that the Regin trojan, which had been referenced in documents leaked by Edward Snowden, had tens of modules that provided it a wide range of capabilities, including keylogging, impersonation, file system forensics and monitoring, network packet capturing, process hooking, system and network information harvesting, credentials theft, and writing and reading emails.

It is unclear exactly who launched the attack on Yandex, but the main suspects are Five Eyes intelligence agencies.

According to Reuters, the attack on Yandex was investigated by Kaspersky, which reportedly found that the attackers, likely tied to Western intelligence, targeted a group of Yandex developers.

This comes shortly after The New York Times reported that the United States had planted potentially destructive malware in Russia’s electric power grid, a claim that President Donald Trump has denied.

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