WORM_GAMARUE.I

 Analysis by: Mark Joseph Manahan

 ALIASES:

Worm:Win32/Gamarue.F (Microsoft), a variant of Win32/Injector.UAE trojan (Eset)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This worm arrives via removable drives. It 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 the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

94,208 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

13 Jul 2012

Arrival Details

This worm arrives via removable drives.

It 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 and executes them:

  • {All User's Profile}\Local Settings\Temp\ms{random characters}.{extension name}

It adds the following possibly malicious files or file components:

  • %User Startup%\A{random number}.exe
  • %User Profile%\Application Data\svchost
  • %User Profile%\Application Data\A{random number}.exe
  • %User Temp%\{random filename}.exe

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.. %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.. %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.)

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 number} = "{All User's Profile}\Local Settings\Temp\ms{random characters}.{random extension}"

It creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
svchost = "%User Profile%\Application Data\svchost"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
A{random number} = "%User Profile%\Application Data\A{random number}.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\RunOnceEx
A{random number} = "%User Profile%\Application Data\A{random number}.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\RunOnce
A{random number} = "%User Profile%\Application Data\A{random number}.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
reallllllllllybro = "%User Profile%\Application Data\svchost"

Propagation

This worm drops the following copy(ies) of itself in all removable drives:

  • svchost

Other Details

This worm connects to the following possibly malicious URL:

  • {BLOCKED}.{BLOCKED}.124.115

It deletes the initially executed copy of itself

NOTES:

This worm uses any of the following extension names for its dropped copy:

  • bat
  • cmd
  • com
  • exe
  • pif
  • scr

It moves the files from {drive letter}:\ to a created sub-folder {driver letter}:\{user name}-reallllllllllybro. It modifies the attributes of the moved files into Hidden to trick users into thinking that the files have been deleted.

  SOLUTION

Minimum Scan Engine:

9.200

FIRST VSAPI PATTERN FILE:

9.292.04

FIRST VSAPI PATTERN DATE:

29 Jul 2012

VSAPI OPR PATTERN File:

9.293.00

VSAPI OPR PATTERN Date:

30 Jul 2012

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

Scan your computer with your Trend Micro product and note files detected as WORM_GAMARUE.I

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • reallllllllllybro = "%User Profile%\Application Data\svchost"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • svchost = "%User Profile%\Application Data\svchost"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • A{random number} = %User Profile%\Application Data\A{random number}.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce
    • A{random number} = %User Profile%\Application Data\A{random number}.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnceEx
    • A{random number} = %User Profile%\Application Data\A{random number}.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • {random number} = "{All User's Profile}\Local Settings\Temp\ms{random characters}.{random extension}"

Step 5

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.
  • {driver letter}:\{user name}-reallllllllllybro

Step 6

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.  
  • %User Startup%\A{random number}.exe
  • %User Profile%\Application Data\svchost
  • %User Profile%\Application Data\A{random number}.exe
  • %User Temp%\{random filename}.exe

Step 7

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

NOTES:

Before proceeding to Step 5, do the following:

To unhide the files hidden by this malware, perform the following steps:

  1. Open Command Prompt.
  2. Click Start>Programs>Accessories>Command Prompt
  3. For every removable drive in the computer, type the following command:

    attrib -h {drive letter}:\*.* /s /d
    Close Command Prompt by typing the following command:
    exit

To restore the moved files by this malware, perform the following steps:

  1. Open {driver letter}:\{user name}-reallllllllllybro and copy the files.
  2. Copy the files from {driver letter}:\{user name}-reallllllllllybro to {driver letter}:\

The created folder {driver letter}:\{user name}-reallllllllllybro is deleted after the files in the said folder has been restored/copied by the user.


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