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BKDR_SMALL.LKA

October 20, 2012
 ALIASES:

Backdoor:Win32/Syrutrk.A (Microsoft); [00003a60.EXE]:BackDoor-DNU (McAfee); Infostealer (Symantec); Trojan-Downloader.Win32.Agent.awot (Kaspersky); BehavesLike.Win32.Malware.ssc (mx-v) (Sunbelt)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 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:

17,920 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

20 Oct 2012

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%\wininet.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It creates the following folders:

  • %User Profile%\Microsoft\Address Book

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CLASSES_ROOT\CLSID\{D7FFD784-5276-42D1-887B-00267870A4C7}\
InProcServer32

HKEY_CURRENT_USER\Software\Microsoft\
WAB\WAB4\Wab File Name

HKEY_CURRENT_USER\Software\RIT\
The Bat!

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%System%\wininet.exe = "%System%\wininet.exe:*:Enabled:Windows XP Update"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\ShellServiceObjectDelayLoad
SysRun = "{D7FFD784-5276-42D1-887B-00267870A4C7}"

HKEY_CURRENT_USER\Software\Microsoft\
WAB\WAB4
OlkContactRefresh = "0"

HKEY_CURRENT_USER\Software\Microsoft\
WAB\WAB4
OlkFolderRefresh = "0"

HKEY_CURRENT_USER\Identities\{8A24C031-62FE-4BF5-94F0-BFD4FBCD674B}
Identity Ordinal = "1"

It modifies the following registry entries:

HKEY_CURRENT_USER\Identities
Identity Ordinal = "2"

(Note: The default value data of the said registry entry is 1.)

Dropping Routine

This backdoor drops the following files:

  • %User Profile%\Address Book\Wilbert.wab

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

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.

  • In HKEY_CLASSES_ROOT\CLSID\{D7FFD784-5276-42D1-887B-00267870A4C7}
    • InProcServer32
  • In HKEY_CURRENT_USER\Software\Microsoft\WAB\WAB4
    • Wab File Name
  • In HKEY_CURRENT_USER\Software\RIT
    • The Bat!

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\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %System%\wininet.exe = "%System%\wininet.exe:*:Enabled:Windows XP Update"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\ShellServiceObjectDelayLoad
    • SysRun = "{D7FFD784-5276-42D1-887B-00267870A4C7}"
  • In HKEY_CURRENT_USER\Software\Microsoft\WAB\WAB4
    • OlkContactRefresh = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\WAB\WAB4
    • OlkFolderRefresh = "0"
  • In HKEY_CURRENT_USER\Identities\{8A24C031-62FE-4BF5-94F0-BFD4FBCD674B}
    • Identity Ordinal = "1"

Step 4

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_CURRENT_USER\Identities
    • From: Identity Ordinal = "2"
      To: Identity Ordinal = ""1""

Step 5

Search and delete this file

[ 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.
  • %User Profile%\Address Book\Wilbert.wab

Step 6

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %User Profile%\Microsoft\Address Book

Step 7

Scan your computer with your Trend Micro product to delete files detected as BKDR_SMALL.LKA. 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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