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TROJ_COBRA.TG

May 07, 2013
 ALIASES:

VirTool:Win32/CeeInject (Microsoft); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse Adload_r.AQG (AVG)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This Trojan 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:

159,293 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

07 May 2013

Arrival Details

This Trojan 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 Trojan drops the following copies of itself into the affected system:

  • %User Temp%\csrss.exe

(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.)

It creates the following folders:

  • %System Root%\DOCUME~1
  • %System Root%\DOCUME~1\ADMINI~1
  • %User Profile%\LOCALS~1
  • %User Profile%\Application Data\{A9CB6A07-5A0A-45ED-ADDC-FCFF85B57575}

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

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Microsoft Windows Hosting Service = "%User Temp%\csrss.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Microsoft Windows Hosting Service = "%User Temp%\csrss.exe"

Other System Modifications

This Trojan modifies the following file(s):

  • %User Profile%\Application Data\Microsoft

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

It deletes the following files:

  • %User Temp%\nsp1.tmp
  • %User Temp%\csrss.exe
  • %User Temp%\nsz3.tmp

(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.)

It adds the following registry keys:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\Run

HKEY_CURRENT_USER\System\CurrentControlSet\
Services\Run

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Policies\
Associations

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Run
Windows RPC Host Service = "%User Temp%\csrss.exe"

HKEY_CURRENT_USER\System\CurrentControlSet\
Services\Run
Windows RPC Host Service = "%User Temp%\csrss.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Microsoft Windows Firewall Service = "%User Temp%\csrss.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Winlogon
Microsoft Windows Firewall Service = "%User Temp%\csrss.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Associations
DefaultFileTypeRisk = "3333"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Associations
LowRiskFileTypes = ".exe"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
Microsoft Windows Hosting Service = "%User Temp%\csrss.exe"

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\nsp2.tmp
  • %User Temp%\rigoxiceva.dll
  • %User Temp%\Lequvasuqet.dll
  • %User Temp%\kavimoxepe.dll
  • %User Temp%\Manekinocece.Lij
  • %User Temp%\Diziweriki.dll
  • %User Temp%\layubexovecu.exe
  • %User Profile%\Microsoft\Crypto
  • %User Profile%\Crypto\RSA
  • %User Profile%\RSA\S-1-5-21-4025279379-4087772427-2915903831-500
  • rm.bat
  • %User Temp%\nsz4.tmp

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

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.300

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

Restart in Safe Mode

[ Learn More ]

Step 3

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_LOCAL_MACHINE\System\CurrentControlSet\Services\
    • Run
  • In HKEY_CURRENT_USER\System\CurrentControlSet\Services\
    • Run
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\
    • Associations

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
    • Microsoft Windows Hosting Service = "%User Temp%\csrss.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Microsoft Windows Hosting Service = "%User Temp%\csrss.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Run
    • Windows RPC Host Service = "%User Temp%\csrss.exe"
  • In HKEY_CURRENT_USER\System\CurrentControlSet\Services\Run
    • Windows RPC Host Service = "%User Temp%\csrss.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • Microsoft Windows Firewall Service = "%User Temp%\csrss.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
    • Microsoft Windows Firewall Service = "%User Temp%\csrss.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Associations
    • DefaultFileTypeRisk = "3333"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Associations
    • LowRiskFileTypes = ".exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • Microsoft Windows Hosting Service = "%User Temp%\csrss.exe"

Step 5

Search and delete these components

[ Learn More ]
There may be some components 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%\nsp2.tmp
  • %User Temp%\rigoxiceva.dll
  • %User Temp%\Lequvasuqet.dll
  • %User Temp%\kavimoxepe.dll
  • %User Temp%\Manekinocece.Lij
  • %User Temp%\Diziweriki.dll
  • %User Temp%\layubexovecu.exe
  • %User Profile%\Microsoft\Crypto
  • %User Profile%\Crypto\RSA
  • %User Profile%\RSA\S-1-5-21-4025279379-4087772427-2915903831-500
  • rm.bat
  • %User Temp%\nsz4.tmp

Step 6

Search and delete these folders

[ 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.
  • %System Root%\DOCUME~1
  • %System Root%\DOCUME~1\ADMINI~1
  • %User Profile%\LOCALS~1
  • %User Profile%\Application Data\{A9CB6A07-5A0A-45ED-ADDC-FCFF85B57575}

Step 7

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

Step 8

Restore deleted/modified files and/or registry entries from backup

*Note: Only Microsoft-related files/keys/values will be restored. If this malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

    • %User Profile%\Application Data\Microsoft

Step 9

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %User Temp%\nsp1.tmp
  • %User Temp%\csrss.exe
  • %User Temp%\nsz3.tmp


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