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WORM_PERLOVGA.G

Overview

Malware type: Worm

Aliases: PAK:PE_Patch, PAK:MEW, Worm.Win32.Perlovga.a (Kaspersky), W32/Perlovga (McAfee), W32.SillyFDC (Symantec), W32/Perlovga.A.1 (Avira), W32/Perlovga.A (exact) (F-Prot), W32/Perlovg-D (Sophos), Worm:Win32/Perlovga.A (Microsoft)

In the wild: Yes

Destructive: No

Language: English

Platform: Windows 98, ME, NT, 2000, XP, Server 2003

Encrypted: No

Overall risk rating:

Reported infections:

Damage potential:

High

Distribution potential:

Medium

Infection Channel 1 : Propagates via removable drives


Infection Channel 2 : Copies itself in all available physical drives


Description: 

This worm may be dropped by other malware. It may arrive bundled with malware packages as a malware component. It may be installed manually by a user. It may be downloaded unknowingly by a user when visiting malicious Web sites.

It drops copies of itself. It drops files/components. Trend Micro detects its component file as BKDR_SMALL.DDE. It then executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

It modifies registry entries to enable its automatic execution at every system startup.

It drops copies of itself in all physical and removable drives. It drops an AUTORUN.INF file to automatically execute dropped copies when the drives are accessed.

For additional information about this threat, see:

Description created: Jun. 29, 2008 1:47:02 AM GMT -0800


Technical Details

File type: PE

Memory resident:  Yes

Size of malware: Varies

Initial samples received on: Jun 26, 2008

Related toBKDR_SMALL.DDE

Payload 1: Drops files

Details:

Arrival, Installation, and Autostart Technique

This worm may be dropped by other malware. It may arrive bundled with malware packages as a malware component. It may be installed manually by a user. It may be downloaded unknowingly by a user when visiting malicious Web sites.

It drops the following files:

  • %System%\temp{0-9}.exe - component detected as BKDR_SMALL.DDE
  • %Windows%\xcopy.exe - copy of itself

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT. %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.)

It then executes the dropped component. As a result, malicious routines of the dropped backdoor are exhibited on the affected system.

It modifies the following registry entry(ies) to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\Windows NT\
CurrentVersion\Windows
Load = "%Windows%\svchost.exe"

(Note: The default value data for the said registry entry is blank.)

Propagation via Physical/Removable/Floppy Drives

This worm drops copies of itself in all physical and removable drives as COPY .EXE. It also drops an AUTORUN.INF file to automatically execute dropped copies when the drives are accessed.

The said .INF file contains the following strings:

[AutoRun]
Shellexecute=copy.exe

Other Details

This worm searches the affected system's root folder (usually C:\) for the following files:

  • autorun.inf
  • host.exe

If found, it attempts to copy these files into the Windows folder. It renames HOST.EXE to SVCHOST.EXE once copied in the Windows folder.

It runs on Windows 98, ME, NT, 2000, XP, and Server 2003.

Analysis By: Jasen Sumalapao

Revision History:

First pattern file version: 5.374.11
First pattern file release date: Jun 29, 2008

Solution

Minimum scan engine version needed: 8.500

Pattern file needed: 8.511.00

Pattern release date: Oct 20, 2011


Important note: The "Minimum scan engine" refers to the earliest Trend Micro scan engine version guaranteed to detect this threat. However, Trend Micro strongly recommends that you update to the latest version in order to get comprehensive protection. Download the latest scan engine here.

Solution:

Note: To fully remove all associated malware, perform the clean solution for BKDR_SMALL.DDE.

Important Windows ME/XP Cleaning Instructions

Users running Windows ME and XP must disable System Restore to allow full scanning of infected computers.

Users running other Windows versions can proceed with the succeeding solution set(s).

Restarting in Safe Mode

This malware has characteristics that require the computer to be restarted in safe mode. Go to this page for instructions on how to restart your computer in safe mode.

Restoring Modified Entry from the Registry

This solution deletes/modifies registry keys/entries added/modified by this malware. Before performing the steps below, make sure you know how to back up the registry and how to restore it if a problem occurs. Refer to this Microsoft article for more information about modifying your computer's registry.

  1. Open Registry Editor. Click Start>Run, type REGEDIT, then press Enter.
  2. In the left panel, double-click the following:
    HKEY_CURRENT_USER>Software>Microsoft>
    Windows>CurrentVersion>Run
  3. In the right panel, locate the entry:
    Load = "%Windows%\svchost.exe"
    (Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)
  4. Right-click on the value name and choose Modify. Delete the value data of this entry.
  5. Close Registry Editor.

Deleting Malware-created AUTORUN.INF/s

  1. Right-click Start then click Search... or Find..., depending on the version of Windows you are running.
  2. In the Named input box, type:
    AUTORUN.INF
  3. In the Look In drop-down list, select a drive, then press Enter.
  4. Select the file, then open using Notepad.
  5. Check if the following lines are present in the file:
    [AutoRun]
    Shellexecute=copy.exe
  6. If the lines are present, delete the file.
  7. Repeat steps 3 to 6 for AUTORUN.INF files in the remaining removable drives.
  8. Close Search Results.

Running Trend Micro Antivirus

Restart your computer normally before performing the following solution.

Scan your computer with Trend Micro antivirus and delete files detected as WORM_PERLOVGA.G. To do this, Trend Micro customers must download the latest virus pattern file and scan their computers. Other Internet users can use HouseCall, the Trend Micro online threat scanner.




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