WORM_AMBLER.A

October 08, 2012
 Analysis by: jasperm
 PLATFORM:

Windows 2000, XP, Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Propagates via removable drives, Copies itself in all available physical drives

It drops AUTORUN.INF file to enable the automatic execution of the main executable file whenever infected drives are accessed.

This worm may be dropped by other malware.

It acts as a Browser Helper Object (BHO) that monitors a user's Internet-browsing habits.

It disables Task Manager, Registry Editor, and Folder Options.

It logs a user's keystrokes to steal information. It sends the information it gathers to remote sites.

  TECHNICAL DETAILS

File Size:

34,304 bytes

File Type:

PE

Memory Resident:

Yes

Initial Samples Received Date:

20 Sep 2010

Payload:

Steals information

Arrival Details

This worm may be dropped by other malware.

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{1A43B51D-2671-4bcc-89F0-9BC42DB29016}
StubPath = rundll32 {malware name}.DLL,InitO

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
dcom = rundll32.exe {malware name}.DLL,ID

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{1A43B51D-2671-4bcc-89F0-9BC42DB29016}
(Default) = DCOM service

It adds the following registry entries to install itself as a Browser Helper Object (BHO):

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects\{C2C3339C-2559-4b81-B9EF-CBAF906D5DA2}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{C2C3339C-2559-4b81-B9EF-CBAF906D5DA2}
InProcServer32 = {malware name}.DLL

It acts as a Browser Helper Object (BHO) that monitors a user's Internet-browsing habits.

Other System Modifications

This worm adds the following registry keys as part of its installation routine:

HKEY_LOCAL_MACHINE\SOFTWARE\Firefox

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{1A43B51D-2671-4bcc-89F0-9BC42DB29016}

It creates the following registry entry(ies) to disable Task Manager, Registry Tools and Folder Options:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = 1

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableRegistryTools = 1

Propagation

The said .INF file contains the following strings:

[AutoRun]
open=RECYCLER\recycld.exe
icon=%System%\SHELL32.dll,4
action=Open folder to view files
shell\open=Open
shell\open\command=RECYCLER\recycld.exe
shell\open\default=1

(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.)

Information Theft

This worm logs a user's keystrokes to steal information.

It sends the information it gathers to remote sites.

Stolen Information

The stolen information is saved in the following file:

  • ns2.txt
  • cds.txt
  • al.txt
  • i2.txt
  • r2.txt
  • e3.txt
  • r24.txt
  • p1.txt
  • eas.txt
  • dz1.txt
  • sdd.txt
  • bxx.txt
  • bs.txt

Other Details

This worm does the following:

  • Steals information from the following:
    • MSN Explorer signup credentials
    • IE password-protected sites
    • IE auto-complete fields
    • Auto-complete passwords
    • Protected storage
    • Outlook Express
    • Cookies
    • Certificates

  SOLUTION

Minimum Scan Engine:

8.900

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_AMBLER.A

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

To enable Registry Editor, Task Manager, and Folder options:

  1. Open Notepad. To do this, click Start>Run, type Notepad in the text box provided, then press Enter.
  2. Copy and paste the following script:
  3. Save this file as C:RESTORE.VBS.
  4. Click Start>Run again, type C:RESTORE.VBS in the text box provided, then press Enter.
  5. Click Yes at the prompt of the message box to execute the .VBS file.

Step 5

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\RunOnce
    • dcom = rundll32.exe {malware name}.DLL,ID
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
    • DisableTaskMgr = 1
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
    • DisableRegistryTools = 1

Step 6

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects
    • {C2C3339C-2559-4b81-B9EF-CBAF906D5DA2}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID
    • {C2C3339C-2559-4b81-B9EF-CBAF906D5DA2}
  • In HKEY_LOCAL_MACHINE\SOFTWARE
    • Firefox
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components
    • {1A43B51D-2671-4bcc-89F0-9BC42DB29016}

Step 7

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.
  • ns2.txt
  • cds.txt
  • al.txt
  • i2.txt
  • r2.txt
  • e3.txt
  • r24.txt
  • p1.txt
  • eas.txt
  • dz1.txt
  • sdd.txt
  • bxx.txt
  • bs.txt

Step 8

Search and delete AUTORUN.INF files created by WORM_AMBLER.A that contain these strings

[ Learn More ]
[AutoRun]
open=RECYCLER\recycld.exe
icon=%System%\SHELL32.dll,4
action=Open folder to view files
shell\open=Open
shell\open\command=RECYCLER\recycld.exe
shell\open\default=1

Step 9

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