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WORM_MAINBOT.BO

March 17, 2011
 Analysis by: Erika Mendoza
 PLATFORM:

Windows 2000, Windows XP, Windows 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

This worm adds registry entries to enable its automatic execution at every system startup.

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

It executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

  TECHNICAL DETAILS

File Size:

43,615 bytes

File Type:

PE

Memory Resident:

Yes

Initial Samples Received Date:

03 Mar 2011

Payload:

Connects to URLs/Ips, Downloads files

Installation

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

  • %System Root%\RECYCLER\R-1-5-21-1482476501-1644491937-682003330-1013\acleaner.exe

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It drops the following non-malicious file:

  • %System Root%\RECYCLER\R-1-5-21-1482476501-1644491937-682003330-1013\Desktop.ini

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It creates the following folders:

  • %System Root%\RECYCLER\R-1-5-21-1482476501-1644491937-682003330-1013
  • [drive letter]:\RECYCLER\R-1-5-21-1482476501-1644491937-682003330-1013
  • [drive letter]:\RECYCLER

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Taskman = "%System Root%\RECYCLER\R-1-5-21-1482476501-1644491937-682003330-1013\acleaner.exe"

Propagation

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

  • RECYCLER\R-1-5-21-1482476501-1644491937-682003330-1013\acleaner.exe

It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

It modifies the contents of an existing AUTORUN.INF file to automatically execute its dropped copy. It does this by adding the following strings in the .INF file:

  • {garbage characters}
    [AutoRun]
    open=RECYCLER\R-1-5-21-1482476501-1644491937-682003330-1013\acleaner.exe
    {garbage characters}
    icon=%System Root%\system32\SHELL32.dll,4
    action=Open folder to view files
    shell\open=Open
    shell\open\command=RECYCLER\R-1-5-21-1482476501-1644491937-682003330-1013\acleaner.exe
    {garbage characters}
    shell\open\default=1
    {garbage characters}

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

Download Routine

This worm connects to the following Web site(s) to download and execute a malicious file:

  • http://one.{BLOCKED}raoi.com/ms.exe
  • http://two.{BLOCKED}raoi.com/serv8.exe
  • http://two.{BLOCKED}raoi.com/dq.exe

It saves the files it downloads using the following names:

  • %UserProfile%\96.exe - detected as WORM_KOLAB.FH
  • %UserProfile%\betd.exe - detected as TROJ_FAKEAV.SM8
  • %UserProfile%\fedw.exe - detected as BKDR_OLEVAP.A

It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

  SOLUTION

Minimum Scan Engine:

8.900

Step 1

For Windows ME and XP users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Remove malware files dropped/downloaded by WORM_MAINBOT.BO

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 NT\CurrentVersion\Winlogon
    • Taskman = %System Root%\RECYCLER\R-1-5-21-1482476501-1644491937-682003330-1013\acleaner.exe

Step 5

Search and delete AUTORUN.INF files created by WORM_MAINBOT.BO that contain these strings

[ Learn More ]
{garbage characters}
[AutoRun]
open=RECYCLER\R-1-5-21-1482476501-1644491937-682003330-1013\acleaner.exe
{garbage characters}
icon=%System Root%\system32\SHELL32.dll,4
action=Open folder to view files
shell\open=Open
shell\open\command=RECYCLER\R-1-5-21-1482476501-1644491937-682003330-1013\acleaner.exe
{garbage characters}
shell\open\default=1
{garbage characters}

Step 6

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.
  • %System Root%\RECYCLER\R-1-5-21-1482476501-1644491937-682003330-1013
  • [drive letter]:\RECYCLER\R-1-5-21-1482476501-1644491937-682003330-1013
  • [drive letter]:\RECYCLER

Step 7

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