BKDR_ANDROM.GK

August 12, 2013
 Analysis by: Jennifer Gumban
 ALIASES:

VirTool:Win32/VBInject.gen!JD (Microsoft), Trojan-Dropper.Win32.Dorifel.afpu (Kaspersky), Downloader.Dromedan (Norton)

 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:

  • 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 modifies the Internet Explorer Zone Settings.

  TECHNICAL DETAILS

File Size:

126,976 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

17 Jul 2013

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 file(s)/component(s):

  • %TEMP%\{Random File Name}.bat
  • %Application Data%\{Random Folder Name}\{Random File Name}.{Random File Extension}

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)

It drops the following copies of itself into the affected system:

  • %All Users Profile%\svchost.exe
  • %All Users Profile%\{Random File Name}.exe
  • %Application Data%\{Random Folder Name}\{Random File Name}.exe
  • %TEMP%\{Random File Name}.exe

(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.. %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)

It terminates the execution of the copy it initially executed and executes the copy it drops instead.

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"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{Random GUID} = "%Application Data%\{Random Folder Name}\{Random File Name}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
{Random Key Name}
{Random Subkey} = "{Random Hex Values}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
{Random Numbers} = "%All Users Profile%\{Random File Name}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Windows
Load = "%User Temp%\{Random File Name}.{Extension name}"

Other System Modifications

This backdoor adds the following registry entries:

HKEY_CURRENT_USER\Identities
Identity Ordinal = "2"

HKEY_CURRENT_USER\Identities\{Random GUID}
Identity Ordinal = "1"

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

HKEY_LOCAL_MACHINE\SYSTEM\{Current Control Set}\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile\AuthorizedApplications\
List
%Windows%\explorer.exe = "%Windows%\explorer.exe"

HKEY_LOCAL_MACHINE\SYSTEM\{Current Control Set}\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%Windows%\explorer.exe = "%Windows%\explorer.exe"

HKEY_LOCAL_MACHINE\SYSTEM\{Current Control Set}\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%System%\msiexec.exe = "%System%\msiexec.exe:*:Generic Host Process"

HKEY_LOCAL_MACHINE\SYSTEM\{Current Control Set}\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%System%\svchost.exe = "%System%\svchost.exe:*:Generic Host Process"

Web Browser Home Page and Search Page Modification

This backdoor modifies the Internet Explorer Zone Settings.

Other Details

This backdoor connects to the following possibly malicious URL:

  • http://{BLOCKED}t.pl/orders.php
  • http://{BLOCKED}y.ru/black.php
  • http://{BLOCKED}ales.pl/buy.php
  • http://{BLOCKED}udio.pl

NOTES:
When BKDR_ANDROM.GK is run on Windows Vista and Windows 7, it drops a copy of itself as %System Root%\Users\All Users\svchost.exe and %System Root%\Program Data\svchost.exe

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

10.164.02

FIRST VSAPI PATTERN DATE:

19 Jul 2013

VSAPI OPR PATTERN File:

10.165.00

VSAPI OPR PATTERN Date:

20 Jul 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.GK

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\Run
    • SunJavaUpdateSched = "%All Users Profile%\svchost.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {Random GUID} = "%Application Data%\{Random Folder Name}\{Random File Name}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\{Random Key Name}
    • {Random Subkey} = "{Random Hex Values}"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • {Random Numbers} = "%All Users Profile%\{Random File Name}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows
    • Load = "%User Temp%\{Random File Name}.{Extension name}"
  • In HKEY_CURRENT_USER\Identities
    • Identity Ordinal = "2"
  • In HKEY_CURRENT_USER\Identities\{Random GUID}
    • Identity Ordinal = "1"
  • In HKEY_LOCAL_MACHINE\SYSTEM\{Current Control Set}\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile\AuthorizedApplications\List
    • %Windows%\explorer.exe = "%Windows%\explorer.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\{Current Control Set}\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %Windows%\explorer.exe = "%Windows%\explorer.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\{Current Control Set}\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %System%\msiexec.exe = "%System%\msiexec.exe:*:Generic Host Process"
  • In HKEY_LOCAL_MACHINE\SYSTEM\{Current Control Set}\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %System%\svchost.exe = "%System%\svchost.exe:*:Generic Host Process"

Step 5

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.
  • %TEMP%\{Random File Name}.bat
  • %Application Data%\{Random Folder Name}\{Random File Name}.{Random File Extension}

Step 6

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