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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
Platform: Windows 98, ME, NT, 2000, XP, Server 2003
Overall risk rating:
Infection Channel 1 : Propagates via removable drives
Infection Channel 2 : Copies itself in all available physical drives
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
File type: PE
Memory resident: Yes
Size of malware: Varies
Initial samples received on: Jun 26, 2008
Related to: BKDR_SMALL.DDE
Arrival, Installation, and Autostart Technique
It drops the following files:
(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:
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:
This worm searches the affected system's root folder (usually C:\) for the following files:
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
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.
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.
Deleting Malware-created AUTORUN.INF/s
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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