- 562a75d033a21ef179495f5b6cb8b26a2a372fd7 (update.bin)
- d3a7dbb4c0a53e95b427a742e187e080cdf0cce7 (svcnost.exe)
A mining Trojan installing itself on the system via the update mechanism of the “Kompiuternyi Zal” program designed to automate computer clubs and cybercafes (ComputerZal.exe (c993afee1c577460d21d544d10d5f74ef18eb0b4)). This program periodically sends a POST request to a PHP script at http://astrumsoft.com/compzal/new_version_check.php. This request contains an application version number and information about the computer.
The server’s response looks as follows:
4.45 710 [-] Described how to configure the automatic log on to system (so computer will not ask for password after reboot/sleep) [*] "Time out" status shows up to client computers with remaining debt only, otherwise it automatically becomes "Free" <ENDCOMMENT>
This response with the cut <ENDCOMMENT> string is processed further. In the example, 710 is a command identifier the Trojan uses to perform different actions. For identifiers 800..809, the update.bin file is downloaded from the astrumsoft.com server and saved to the %temp% folder with the "cztemp" or "czt" prefixes. The file name “update.bin” is obfuscated in the code and added to the URL symbol-by-symbol.
For identifier 805, the update.bin file is downloaded and executed.
Once the update.bin program is launched, it closes all "svchostm.exe" and "svcnost.exe" processes, saves the "svcnost.exe" file to the disk and modifies the system registry key [HKLM\Software\Microsoft\Windows\CurrentVersion\Run] to enable automatic execution of the file. In this key, the program registers the 'svchostm’ key. The "svcnost.exe" application is a miner. Data on the wallet, where the mined cryptocurrency is transferred, is hardcoded in the Trojan’s body. The workers’ names for the examined Trojan sample have the "soyuz6_" prefix. The prefix is stored in the malware’s body.