BKDR_ZEGOST.EY
Trojan:Win32/ServStart!rfn (Microsoft); SMG.Heur!gen (Symantec); Trojan.Win32.StartServ.xer (Kaspersky)
Windows
Threat Type: Backdoor
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
It deletes the initially executed copy of itself.
TECHNICAL DETAILS
Arrival Details
This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
Installation
This backdoor drops the following copies of itself into the affected system and executes them:
- %System%\{Malware name}.exe - set attributes to Hidden and System
- %System%\vmtoolsd.exe - set attributes to Hidden and System
(Note: %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)
It adds the following mutexes to ensure that only one of its copies runs at any one time:
- 79
Autostart Technique
This backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\79
ImagePath = %System%\{Malware name}.exe
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\79
DisplayName = Microsoft Software 79
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\79
Description = Thank you for use 79
It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\79
Backdoor Routine
This backdoor connects to the following URL(s) to send and receive commands from a remote malicious user:
- {BLOCKED}.{BLOCKED}.244.30
uses port 48080
It posts the following information to its command and control (C&C) server:
- Current usage of both physical and virtual memory
- OS version information
- Processor information
Other Details
This backdoor deletes the initially executed copy of itself
SOLUTION
Step 1
Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.
Step 2
Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.
Step 3
Restart in Safe Mode
Step 4
Delete this registry key
Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.
- In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet001\Services
- 79
- 79
Step 5
Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_ZEGOST.EY. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.
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