Analysis by: kathleenno
ALIASES:

Trojan.Dropper (Symantec); Trojan:Win32/Rimecud.A (Microsoft); Trojan.Win32.Pincav.axfo (Kaspersky); Generic.dx!zhd (Mcafee); Mal/Generic-L (Sophos); W32/Rimecud.AJ (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

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

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 a website to send and receive information.

  TECHNICAL DETAILS

File Size: 66,048 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 22 Jun 2011
Payload: Connects to URLs/IPs, Compromises system security

Arrival Details

This worm 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%\sylwpx.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.)

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 = "%Application Data%\sylwpx.exe"

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:

  • Launch TCP or UDP flood
  • Propagate itself via removable drives

It connects to the following websites to send and receive information:

  • {BLOCKED}f.{BLOCKED}8.com
  • {BLOCKED}2.{BLOCKED}8.com
  • {BLOCKED}3.{BLOCKED}8.com
  • {BLOCKED}4.{BLOCKED}8.com
  • {BLOCKED}5.{BLOCKED}8.com

  SOLUTION

Minimum Scan Engine: 8.900

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

Restart in Safe Mode

[ 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 = "%Application Data%\sylwpx.exe"

Step 4

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