BKDR_ANDROM.ET

 Analysis by: Nikko Tamana

 ALIASES:

W32/Androm.DW!tr (Fortinet), Backdoor.Win32.Androm (Ikarus), Backdoor.Win32.Androm.gz (Kaspersky), Worm:Win32/Gamarue.I (Microsoft)

 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:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • 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 executes then deletes itself afterward.

  TECHNICAL DETAILS

File Size:

60,416 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

21 May 2013

Payload:

Compromises system security, 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%\ms{random characters}.{file extension}
  • %All Users Profile%\svchost.exe - If 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.)

It executes then deletes itself afterward.

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
SunJavaUpdateSched = "%All Users Profile%\svchost.exe" - If running in virtual machine

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
{random number} = "%All Users Profile%\ms{random characters}.{file extension}"

Other System Modifications

This backdoor adds the following registry keys as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run

It 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}"

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}d.pl/image.php
  • http://{BLOCKED}a.pl/image.php
  • http://{BLOCKED}e.pl/image.php
  • http://{BLOCKED}m.ru/image.php
  • http://{BLOCKED}ge.com/image.php

NOTES:

Where {file extension} is any of the following:

  • BAT
  • CMD
  • COM
  • EXE
  • PIF
  • SCR

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:

9.932.05

FIRST VSAPI PATTERN DATE:

21 May 2013

VSAPI OPR PATTERN File:

9.933.00

VSAPI OPR PATTERN Date:

22 May 2013

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.ET

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Delete this registry key

[ 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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer
    • Run

Step 5

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
    • SunJavaUpdateSched = "%All Users Profile%\svchost.exe" - If running in virtual machine
  • 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 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.
  • %All Users Profile%\ms{random characters}.{file extension}
  • %All Users Profile%\svchost.exe - If running in virtual machine

Step 7

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