Analysis by: Jennifer Gumban
 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet

This Worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It deletes registry entries, causing some applications and programs to not function properly.

  TECHNICAL DETAILS

Payload: Connects to URLs/IPs

Arrival Details

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

  • %All Users Profile%\ms{random}.exe

(Note: %All Users Profile% is the All Users folder, where it usually is C:\Documents and Settings\All Users on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\ProgramData on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It drops the following files:

  • %All User Profile%\ms{random number}.dat
  • %User Temp%\KB{8 random numbers}.exe
  • %User Temp%\cdo{random number}.dll

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

It adds the following processes:

  • msiexec.exe

It injects codes into the following process(es):

  • created "msiexec.exe"

Autostart Technique

This Worm 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 Numbers} = "%All Users Profile%\ms{random}.exe"

Other System Modifications

This Worm also creates the following registry entry(ies) as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = "2"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = "0"

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Windows
Load = ""

HKEY_CURRENT_USER\Software\Microsoft\
Windows
{Random Numbers} = "{Encrypted Data}"

HKEY_CURRENT_USER\Keyboard Layout
1 = "{Encrypted Data}"

HKEY_CURRENT_USER\Keyboard Layout
2 = "{Encrypted Data}"

It deletes the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Image File Execution Options\
taskmgr.exe
Debugger = "taskmgr.exe"

Other Details

This Worm connects to the following URL(s) to check for an Internet connection:

  • yahoo.com
  • google.com
  • bing.com
  • update.microsoft.com
  • microsoft.com

It does the following:

  • Checks if it is being run in a virtual environment or emulation software. If so, it will perform infinite sleep.

  SOLUTION

Minimum Scan Engine: 9.850

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

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\Policies\Explorer\Run
    • {Random Numbers} = "%All Users Profile%\ms{random}.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • Hidden = "2"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • ShowSuperHidden = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows
    • Load = ""
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows
    • {Random Numbers} = "{Encrypted Data}"
  • In HKEY_CURRENT_USER\Keyboard Layout
    • 1 = "{Encrypted Data}"
  • In HKEY_CURRENT_USER\Keyboard Layout
    • 2 = "{Encrypted Data}"

Step 5

Search and delete this file

[ 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 User Profile%\ms{random}.exe
%All User Profile%\ms{random number}.dat
%User Temp%\KB{8 random numbers}.exe
%User Temp%\cdo{random number}.dll

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_GAMARUE.YYPG. 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 7

Restore this deleted registry key/value from backup

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

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\taskmgr.exe
    • Debugger = "taskmgr.exe"


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