A malicious program designed to inject arbitrary content into webpages loaded in browser windows.
Once launched, it determines the infected computer ID based on the data on equipment, computer name, and current user name.
Then it copies its executable file into
C:\Users\<username>\My Documents\MyApplicationData\~backup.exe
and modifies the system registry as follows:
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run] "~backup~"="C:\Users\<username>\My Documents\MyApplicationData\~backup.exe" specifying the path to the dropper to be deleted as follows: "~tempbackup~"="<path to the dropper>"
On 32-bit systems
The Trojan launches a copy of explorer.exe and gets injected into this copy. Then it reads its own file and deletes the dropper if the file's name does not contain the “~backup” string. Injections are accompanied by modification of the following file:
C:\Users\<username>\My Documents\MyApplicationData\~backup.dat
On 64-bit systems
The Trojan modifies the system registry branch that manages the autorun list, runs its executable file and its own copy, and deletes the dropper's file. The malicious program verifies the presence of its two copies in the infected computer's memory and of the corresponding entries in the system registry.
Then it scans the system for installed anti-virus programs by looking through the names of active processes.
MsMpEng.exe, msseces.exe, avp.exe, dwengine.exe, dwservice.exe, ecls.exe, egui.exe, ekrn.exe, AvastUI.exe, AvastSvc.exe, avgnt.exe, avguard.exe, avshadow.exe, avgnsx.exe, avgrsx.exe, avgtray.exe, ccsvchst.exe, vba32ldr.exe, vbaScheduler.exe, Mcshield.exe, Mctray.exe, bdagent.exe, coreServiceShell.exe, uiSeAgnt.exe
By checking the names of the following processes, the Trojan attempts to determine whether it is running in a virtual environment or not:
vmtoolsd.exe,vmacthlp.exe,vpcmap.exe,vmsrvc.exe,vmusrvc.exe
Once installed, Trojan.Mayachok.18607 tries to inject itself into all Windows processes, including processes of launched browsers.
The configuration file is saved into c:\Users\<username>\Cookies\cf. Then the Trojan sends requests to a number of addresses and gets a new configuration file, which may contain a command to download an executable file. The executable file is saved into the following folder:
C:\Users\<username>\My Documents\MyApplicationData\~dwnld.exe
After that, the file is run.
Moreover, the configuration file contains a script injected by the Trojan into all webpages browsed by the user.