Successor to NetTraveler Malware Dissected

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A recently observed backdoor could be intended as the successor of the NetTraveler malware, Kaspersky Lab security researchers report.

NetTraveler has been around for more than a decade, but has recently resurfaced in a series of cyber-espionage attacks launched against victims in Russia and neighboring European countries. Several years ago, the malware was associated with a campaign that hit targets in over 40 countries.

The malware was designed for surveillance purposes, and a new variant referred to as Travle or PYLOT appears to have emerged earlier this year. Supposedly the offspring of a Chinese-speaking actor, the new threat gets its name from a typo in a string in one of the analyzed samples: “Travle Path Failed!” (the typo has been corrected in newer releases).

The malware was observed being deployed using malicious documents delivered via spear-phishing attacks on Russian-speaking targets. The executables were maintained in encrypted form using a technique previously used to conceal Enfal, and then the Microcin APT family.

Travle command and control (C&C) domains often overlap with those of Enfal, which in turn was observed using the same encryption method for maintaining the C&C URL as NetTraveler. Thus, Kaspersky believes that Enfal, NetTraveler, Travle and Microcin are related to each other and that the Travle backdoor is the successor of NetTraveler.

Upon initializing communication with its C&C server, the malware sends information about the target operating system in an HTTP POST request. Sent information includes UserID (based on the computer name and IP-address), Computer name, Keyboard layout, OS version, IP-addresses, and MAC address.

The server responds by sending URL paths for receiving commands, for reporting on command execution results, and for downloading and uploading files from C&C. The server also provides the first and second RC4 key, and an ID. After receiving the packet, the backdoor waits for additional commands.

All communication with the server is encrypted, with the ciphering algorithm depending on the type of transmitted object. The bot can send technical messages, which contain information about the OS or about the performed commands, and operational messages, which contain lists of files in a directory or the content of a specific file.

Based on commands received from the C&C, the malware can scan the file system, can execute specified batch file or application with passed arguments, can check if a specified file exists, can delete/rename/move/create files, can download and execute files (scripts or BAT-files), can download DLLs and launch them using the LoadLibrary API function, and can load/unload a library to/from memory.

According to Kaspersky, the actor behind the Travle backdoor has been active during the last few years but doesn’t appear worried about being tracked by security companies. In fact, all of the modifications and new additions they made to their tools have been discovered and detected quite quickly.

“Still, the fact that they didn´t really need to change their TTPs during all these years seems to suggest that they don´t need to increase their sophistication level in order to fulfill their goals. What’s worse, according to subjects of decoy documents these backdoors are used primarily in the CIS region against government organizations, military entities and companies engaged in high-tech research, which indicates that even high-profile targets still have a long way to go to implement IT-sec best practices which efficiently resist targeted attacks,” Kaspersky concludes.