WORM_OSCARBOT.SL

 Analysis by: Sabrina Lei Sioting

 ALIASES:

Backdoor:Win32/IRCbot.FY (Microsoft); Trojan.Win32.Scar.bfca (Kaspersky); W32.Pilleuz!gen13 (Symantec); W32/Autorun.worm.c (McAfee); Mal/TibsPk-A (Sophos); Worm.Win32.Rimecud.a (Sunbelt); P2P-Worm.Win32.Palevo (Ikarus); W32/OscarBot.XY.worm (Panda)

 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

This worm arrives by connecting affected removable drives to a system. 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 drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

  TECHNICAL DETAILS

File Size:

66,560 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

31 May 2010

Arrival Details

This worm arrives by connecting affected removable drives to a system.

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:

  • %Application Data%\afd.exe

(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Windows\Profiles\{user name}\Application Data on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Application Data on Windows NT, and C:\Documents and Settings\{user name}\Local Settings\Application Data 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_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Cftmon32 = "%Application Data%\afd.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Terminal Server\
Install\Software\Microsoft\
Windows\CurrentVersion\Run
Cftmon32 = "%Application Data%\afd.exe"

Other System Modifications

This worm creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile\AuthorizedApplications\
List
{malware path}\{malware name}.exe = "{malware path}\{malware name}.exe:*:Enabled:1"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
{malware path}\{malware name}.exe = "{malware path}\{malware name}.exe:*:Enabled:Cftmon32"

Propagation

This worm creates the following folders in all removable drives:

  • Folder
  • Folder\SubFolder

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

  • Folder\SubFolder\file.exe

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

The said .INF file contains the following strings:

;{garbage chracters}
[autorun
;{garbage chracters}
open=Folder\SubFolder\file.exe
icon=%SystemRoot%\system32\SHELL32.dll,4
action=Open folder to view files using Windows Explorer
shell\\open\command=Folder\SubFolder\file.exe
shell\\explore\command=Folder\SubFolder\file.exe
useautoplay=1

  SOLUTION

Minimum Scan Engine:

9.200

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

Identify and terminate files detected as WORM_OSCARBOT.SL

[ Learn More ]
  1. If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  2. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

Step 3

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
    • Cftmon32 = "%Application Data%\afd.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Terminal Server\Install\Software\Microsoft\Windows\CurrentVersion\Run
    • Cftmon32 = "%Application Data%\afd.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile\AuthorizedApplications\List
    • {malware path}\{malware name}.exe = "{malware path}\{malware name}.exe:*:Enabled:1"
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • {malware path}\{malware name}.exe = "{malware path}\{malware name}.exe:*:Enabled:Cftmon32"

Step 4

Search and delete these folders

[ 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.
  • {drive letter}:\Folder

Step 5

Search and delete AUTORUN.INF files created by WORM_OSCARBOT.SL that contain these strings

[ Learn More ]
    {garbage chracters}
    [autorun]
    {garbage chracters}
    open=Folder\SubFolder\file.exe
    icon=%SystemRoot%\system32\SHELL32.dll,4
    action=Open folder to view files using Windows Explorer
    shell\\open\command=Folder\SubFolder\file.exe
    shell\\explore\command=Folder\SubFolder\file.exe
    useautoplay=1

Step 6

Scan your computer with your Trend Micro product to delete files detected as WORM_OSCARBOT.SL. 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.


Did this description help? Tell us how we did.

Related Malware