WORM_PALEVO.ASC


 ALIASES:

Backdoor.Trojan (Symantec); VirTool:Win32/DelfInject.gen!J (Microsoft); Worm.Win32.AutoRun.fqs (Kaspersky); BackDoor-DOQ.gen.e (Mcafee); W32/AutoRun.DJ.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

Infection Channel:

Propagates via removable drives, Propagates via peer-to-peer networks, Propagates via instant messaging applications

This worm arrives via peer-to-peer (P2P) shares. It arrives via removable drives. 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 copies of itself in all removable drives. It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.

It opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system. It runs certain commands that it receives remotely from a malicious user. Doing this puts the affected computer and information found on the computer at greater risk.

It connects to certain websites to send and receive information.

  TECHNICAL DETAILS

File Size:

132,924 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

15 Jun 2011

Payload:

Compromises system security, Sends and receives information

Arrival Details

This worm arrives via peer-to-peer (P2P) shares.

It arrives via removable drives.

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:

  • %System Root%\RECYCLER\{SID}\svchost.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\{SID}\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\{SID}

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

It injects itself into the following processes as part of its memory residency routine:

  • explorer.exe

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\{SID}\svchost.exe"

Propagation

This worm creates the following folders in all removable drives:

  • nvda

It drops copies of itself in all removable drives.

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:

[AutoRun]
shellexecute="nvda\nvda.exe"
UseAutoPlay=1

Backdoor Routine

This worm opens a random port to allow a remote user to connect to the affected system. Once a successful connection is established, the remote user executes commands on the affected system.

It executes the following command(s) from a remote malicious user:

  • download files or updates of itself
  • launch SYN flood
  • propagate via MSN messenger by sending messages containing a link where a copy of itself may be downloaded
  • propagate itself via peer-to-peer networks

Other Details

This worm connects to the following website to send and receive information:

  • mail.{BLOCKED}espace.org
  • {BLOCKED}mania.biz
  • {BLOCKED}mailer-list.com

NOTES:

It may also arrive as a downloaded file from links sent via messages in MSN messenger.

It may also arrive via the following P2P networks:

  • Ares
  • BearShare
  • DC++
  • eMule
  • iMesh
  • Kazaa
  • Limewire
  • Shareaza

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

8.226.10

FIRST VSAPI PATTERN DATE:

15 Jun 2011

VSAPI OPR PATTERN File:

8.227.00

VSAPI OPR PATTERN Date:

15 Jun 2011

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 delete files detected as WORM_PALEVO.ASC using either the Startup Disk or Recovery Console

[ Learn More ]

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • Taskman = "%System Root%\RECYCLER\{SID}\svchost.exe"

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.
  • %System Root%\RECYCLER\{SID}
  • nvda

Step 5

Search and delete AUTORUN.INF files created by WORM_PALEVO.ASC that contain these strings

[ Learn More ]
[AutoRun]
shellexecute=nvda\nvda.exe
UseAutoPlay=1

Step 6

Scan your computer with your Trend Micro product to delete files detected as WORM_PALEVO.ASC. 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.