BKDR_ANDROM.ASM

 Analysis by: Vincent Martin Hermosura

 ALIASES:

Mal/Generic-L (Sophos), Trojan horse Downloader.Small.KTX (AVG), W32/Androm.EMKX!tr.bdr (Fortinet), Worm.Win32.Gamarue (Ikarus), Backdoor.Win32.Androm.emkx (Kaspersky), Worm:Win32/Gamarue.AM (Microsoft), Win32/TrojanDownloader.Wauchos.AD trojan (Nod32), Trojan.Zbot (Norton), TR/Gamarue.A.310 (Antivir)

 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:

Dropped by other malware, Downloaded from the Internet

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 does not have any propagation routine.

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

It does not have any information-stealing capability.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

31,744 bytes

Memory Resident:

Yes

Initial Samples Received Date:

18 Jun 2014

Payload:

Compromises system security, Connects to URLs/IPs, Downloads files

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: %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 entry(ies) to enable its 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 adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
TaskbarNoNotification = "dword:00000000"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
HideSCAHealth = "dword:00000000"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
TaskbarNoNotification = "dword:00000000"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
HideSCAHealth = dword:00000000

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

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

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"

Propagation

This backdoor does not have any propagation routine.

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 websites to send and receive information:

  • http://{BLOCKD}7.com/gate.php

Information Theft

This backdoor does not have any information-stealing capability.

Other Details

This backdoor deletes the initially executed copy of itself

NOTES:

It 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 for performing 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 routine.

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

10.868.08

FIRST VSAPI PATTERN DATE:

17 Jun 2014

VSAPI OPR PATTERN File:

10.869.00

VSAPI OPR PATTERN Date:

17 Jun 2014

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.ASM

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\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplication\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}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run
    • {random number} = "%ProgramData%\{random}.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • {random number} = "{All Users Profile}\{random}.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • SunJavaUpdateSched = "%ProgramData%\svchost.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • SunJavaUpdateSched = "{All Users Profile}\svchost.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • TaskbarNoNotification = "dword:00000000"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • HideSCAHealth = "dword:00000000"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • TaskbarNoNotification = "dword:00000000"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • HideSCAHealth = "dword:00000000"

Step 5

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out 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 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.
  • %User Temp%\{random number}.exe
  • %System Root%\Documents and Settings\All Users\ms{random number}.dat

Step 7

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