ALIASES:

Backdoor:Win32/Zegost.AD, Backdoor:Win32/Zegost.AD, Backdoor:Win32/Zegost.AD, Backdoor:Win32/Zegost. (Microsoft); [000ab110.EXE]:RDN/Generic PWS.y!bcp, [00075110.EXE]:BackDoor-FGQ, [0003f110.EXE]:BackDoor-FGQ, [000 (McAfee); Trojan.Gen (Symantec); HEUR:Trojan.Win32.Generic (Kaspersky); Mal/Zegost-AC, Mal/Zegost-AC, Mal/Zegost-AC, Mal/PWS-AB (Sophos); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse BackDoor.Generic_r.CFG.dropper (AVG)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • 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.

  TECHNICAL DETAILS

File Size: 292,864 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 12 May 2015

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:

  • %System Root%\sott4.exe

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.)

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Hal2 = "%System Root%\sott4.exe"

Dropping Routine

This backdoor drops the following files:

  • %System Root%\Win.EXE
  • %System Root%\lei.EXE
  • %System Root%\leii.EXE
  • %System Root%\leiii.EXE
  • %User Temp%\qq.cfg

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}0.126.49:2014/qq.txt?9282

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.750

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

Restart in Safe Mode

[ Learn More ]

Step 3

Delete this registry value

[ Learn More ]

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\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • Hal2 = "%System Root%\sott4.exe"

Step 4

Search and delete these components

[ Learn More ]
There may be some components that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %System Root%\Win.EXE
  • %System Root%\lei.EXE
  • %System Root%\leii.EXE
  • %System Root%\leiii.EXE
  • %User Temp%\qq.cfg

Step 5

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_ZEGOST.LY. 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.


Did this description help? Tell us how we did.