PlugX RAT Distributed Via Official Game Installers

The computers of gamers in Taiwan and other Asian countries might have been infected with a piece of malware after cybercriminals managed to compromise official installers and updates for a couple of popular online games.

According to Trend Micro, malicious actors bundled the notorious PlugX remote access Trojan (RAT) with League of Legends (LoL) and Path of Exile (PoE) game files. These games are distributed in certain Asian countries by Singapore-based Garena, which has partnerships with game developers such as Electronic Arts, Riot Games and S2 Games.

Garena warned its customers on December 31 that official game files for League of Legends and Path of Exile had been compromised. The breach was first reported by the Hacks in Taiwan (HITCON) security conference.

Garena said it couldn’t find any evidence that payment data, passwords or other personal information had been compromised, but the company advised users to change their passwords and enable two-step authentication on their accounts.

When executed, the compromised game launchers provided by Garena dropped a legitimate launcher, a “cleaner” component designed to overwrite the altered launcher with a genuine one, and a dropper designed to install the PlugX binaries (detected as BKDR_PLUGX.ZTBL-EC). The role of the “cleaner” was most likely to hide traces of malicious activity, researchers said.

“While checking the certificate, we noticed that the hash value applied to the suspect file was VALID, which means that the ‘signing tool’ was used to pair with the compromised binary’s hash. The clean game launcher, on the other hand, has an invalid digital signature,” Trend Micro noted in a blog post.

The security firm says only the Taiwanese versions of the League of Legends and Path of Exile installers were compromised by the attackers so it’s not surprising that most of the victims (82%) were located in Taiwan. However, based on command and control (C&C) server activity, Trend Micro has determined that some of the infected devices were located in Singapore, Thailand, Malaysia, and Hong Kong.

Garena has cleaned up all the game files and Trend Micro has developed a special tool designed to clean up infected computers. The security company said malware activity stopped after Garena issued the warning in late December.

PlugX is highly popular in Asia. The threat, which gives attackers complete control over infected systems, has often been used in advanced persistent threat (APT) campaigns. In fact, a string found in the malware body (“Cooper”) indicates that a threat group involved in APT operations might be behind the Garena attack.

Gamers are increasingly targeted by cybercriminals. In November, security experts warned users about a piece of malware that had been distributed via the chat feature in the online entertainment platform Steam.