WORM_DORKBOT.RNJ

 Analysis by: Jennifer Gumban

 ALIASES:

Worm.Win32.Ngrbot.whb (Kaspersky), Worm:Win32/Dorkbot.I (Microsoft)

 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: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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 modifies the Internet Explorer Zone Settings.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

164,864 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

30 May 2015

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.

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Adobe System Incorporated = "%User Temp%\Adobe\Reader_sl.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{Random Characters} = "%Application Data%\Identities\{Random Characters}.exe"

Web Browser Home Page and Search Page Modification

This worm modifies the Internet Explorer Zone Settings.

Other Details

This worm connects to the following possibly malicious URL:

  • http://{BLOCKED}.{BLOCKED}.71.118/and7.exe
  • http://{BLOCKED}.{BLOCKED}.71.118/nut7.exe

It drops the following file(s)/component(s):

  • %Application Data%\{Random Character}.exe
  • %Application Data%\Identities\{Random Characters}.exe
  • %Application Data%\{Random Characters}
  • %TEMP%\Adobe\Reader_sl.exe
  • %TEMP%\{Random Characters}
  • %Application Data%\Identities\{Random Characters}.exe

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming 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 deletes itself after execution.

  SOLUTION

Minimum Scan Engine:

9.750

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 WORM_DORKBOT.RNJ

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
    • Adobe System Incorporated = "%User Temp%\Adobe\Reader_sl.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {Random Characters} = "%Application Data%\Identities\{Random Characters}.exe"

Step 5

Search and delete these files

[ 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.
  • %Application Data%\{Random Character}.exe
  • %Application Data%\Identities\{Random Characters}.exe
  • %Application Data%\{Random Characters}
  • %TEMP%\Adobe\Reader_sl.exe
  • %TEMP%\{Random Characters}
  • %Application Data%\Identities\{Random Characters}.exe

Step 6

Reset Internet security settings

[ Learn More ]

Step 7

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

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.


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