BKDR_ANDROM.VO

 Analysis by: Sabrina Lei Sioting

 ALIASES:

Trojan.Encpk.Gen.4 (Fsecure), Trojan-PWS.Win32.Tepfer (Ikarus), Trojan-PSW.Win32.Tepfer.srtr (Kaspersky), PWS-Zbot.gen.oj (McAfee), VirTool:Win32/VBInject.gen!LL (Microsoft), Trojan.Zbot (Symantec),

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Downloaded from the Internet, Dropped by other malware


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 executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size:

85,648 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

08 Jan 2014

Payload:

Compromises system security, Connects to URLs/IPs

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:

  • %All Users Profile%\{random}.exe
  • %All Users Profile%\svchost.exe (when running in virtual machine)
  • %ProgramData%\{random}.exe (Windows Vista and higher versions)
  • %ProgramData%\svchost.exe (Windows Vista and higher versions and running in virtual machine)

(Note: %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.. %ProgramData% is a version of the Program Files folder where any user on a multi-user computer can make changes to programs. This is usually C:\ProgramData in Windows Vista and 7, or C:\Program Files on Windows 2000, XP (32-bit), and Server 2003, or C:\Program Files (x86) on Windows XP (64-bit).)

It injects threads into the following normal process(es):

  • svchost.exe

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\Policies\
Explorer\Run
{random number} = "%ProgramData%\{random}.exe" (Windows Vista and higher versions)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
{random number} = "%All Users Profile%\{random}.exe" (Versions lower than Windows Vista)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
SunJavaUpdateSched = "%ProgramData%\svchost.exe" (Windows Vista and higher versions, running in virtual machine and Java update is disabled in startup)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
SunJavaUpdateSched = "%All Users Profile%\svchost.exe" (Versions lower than Windows Vista, running in virtual machine and Java update is disabled in startup)

It modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
SunJavaUpdateSched = "%ProgramData%\svchost.exe" (Windows Vista and higher versions, running in virtual machine and Java update is enabled in startup)

(Note: The default value data of the said registry entry is {Java Installation Folder}\jusched.exe.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
SunJavaUpdateSched = "%All Users Profile%\svchost.exe" (Versions lower than Windows Vista, running in virtual machine and Java update is enabled in startup)

(Note: The default value data of the said registry entry is {Java Installation Folder}\jusched.exe.)

Other System Modifications

This backdoor creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%System%\svchost.exe = "%System%\svchost.exe:*:Generic Host Process"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%System%\msiexec.exe = "%System%\msiexec.exe:*:Generic Host Process"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
{malware path and filename} = "{malware path and filename}:*:Enabled:{malware filename}"

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Download a file from C&C server and save it as %User Temp%\{random number}.exe
  • Download a file from C&C server and save it as %System Root%\Documents and Settings\All Users\ms{random number}.dat and loads it
  • Start a process
  • Uninstall itself
  • Remote command prompt

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}.biz/and/gate.php

NOTES:

This backdoor checks if it is being run in VMWare environment or Emulation software. If it is being run in a VMWare environment or Emulation software, it performs another routine where in it will open Port 8000 and listen for a backdoor command to perform remote shell execution.

It also checks if there is a running network monitoring software in the affected machine. If found, it also performs its other routines.

  SOLUTION

Minimum Scan Engine:

9.700

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

Scan your computer with your Trend Micro product and note files detected as BKDR_ANDROM.VO

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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\Policies\Explorer\Run
    • {random number} = "%ProgramData%\{random}.exe" (Windows Vista and higher versions)
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • {random number} = "%All Users Profile%\{random}.exe" (Versions lower than Windows Vista)
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • SunJavaUpdateSched = "%ProgramData%\svchost.exe" (Windows Vista and higher versions, running in virtual machine and Java update is disabled in startup)
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • SunJavaUpdateSched = "%All Users Profile%\svchost.exe" (Versions lower than Windows Vista, running in virtual machine and Java update is disabled in startup)
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %System%\svchost.exe = "%System%\svchost.exe:*:Generic Host Process"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %System%\msiexec.exe = "%System%\msiexec.exe:*:Generic Host Process"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • {malware path and filename} = "{malware path and filename}:*:Enabled:{malware filename}"

Step 5

Restore this modified 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
    • From: SunJavaUpdateSched = "%ProgramData%\svchost.exe" (Windows Vista and higher versions, running in virtual machine and Java update is enabled in startup)
      To: SunJavaUpdateSched = {Java Installation Folder}\jusched.exe
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • From: SunJavaUpdateSched = "%All Users Profile%\svchost.exe" (Versions lower than Windows Vista, running in virtual machine and Java update is enabled in startup)
      To: SunJavaUpdateSched = {Java Installation Folder}\jusched.exe

Step 6

Search and delete these files

[ Learn More ]
There may be some component files 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. DATA_GENERIC
Note: To do a search for the following files, right-click Start then click Search... or Find..., depending on the version of Windows you are running. For each file to be deleted, type its file name in the Named input box. In the Look In drop-down list, select My Computer, then press Enter.
  • Once located, select the file then press SHIFT+DELETE to permanently delete the file.
  • Repeat the said steps for all files listed.
  • Step 7

    Scan your computer with your Trend Micro product to delete files detected as BKDR_ANDROM.VO. 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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