WORM_PALEVO.EF

 Analysis by: JessaD

 ALIASES:

Trojan:Win32/Rimecud.A (Microsoft); P2P-Worm.Win32.Palevo.boic (Kaspersky)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Propagates via removable drives


This worm attempts to connect to certain URLs. Once a connection is established, it waits for commands from the remote user.

This worm arrives via removable drives. It may be unknowingly downloaded by a user while visiting malicious websites.

It uses the default Windows folder icon to trick users into opening the file. Double-clicking the file executes this malware.

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

However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

205,312 bytes

File Type:

PE

Memory Resident:

Yes

Initial Samples Received Date:

09 Feb 2011

Payload:

Connects to URLs/Ips

Arrival Details

This worm arrives via removable drives.

It may be unknowingly downloaded by a user while visiting malicious websites.

Installation

This worm drops the following copies of itself into the affected system:

  • %User Profile%\{random name}.exe

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

It uses the default Windows folder icon to trick users into opening the file. Double-clicking the file executes this malware.

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • WQqV+10

It injects codes into the following process(es):

  • 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 = %User Profile%\{random name}.exe

Propagation

This worm drops copies of itself into all the removable drives connected to an affected system.

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=ludasambila\\stosamkrila.exe
action=Open folder to see files using Windows Explorer
USEAUTOPLAY=1
open=ludasambila\\stosamkrila.exe
icon=shell32.dll,4
{garbage characters}
shell\\Install\\command=ludasambila\\stosamkrila.exe
shell\\open\\command=ludasambila\\stosamkrila.exe
shell\\explore\\command=ludasambila\\stosamkrila.exe
shell\\open\\command=ludasambila\\stosamkrila.exe

Backdoor Routine

However, as of this writing, the said sites are inaccessible.

Dropping Routine

This worm sets the attributes of its dropped file(s) to the following:

  • Hidden
  • System
  • Read-Only

Other Details

This worm connects to the following possibly malicious URL:

  • jebena.{BLOCKED}olic.su
  • peer.{BLOCKED}losarske.ru
  • teske.{BLOCKED}arke.com
  • juice.{BLOCKED}racala.org

NOTES:
Once a connection is established, it waits for commands from the remote user, which may lead to the following actions:

  • Download another malicious file
  • Hijack search queries

  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

Scan your computer with your Trend Micro product and note files detected as WORM_PALEVO.EF

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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 = %User Profile%\{random name}.exe

Step 5

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

[ Learn More ]
[AutoRun]
shellexecute=ludasambila\\stosamkrila.exe
action=Open folder to see files using Windows Explorer
USEAUTOPLAY=1
open=ludasambila\\stosamkrila.exe
icon=shell32.dll,4
{garbage characters}
shell\\Install\\command=ludasambila\\stosamkrila.exe
shell\\open\\command=ludasambila\\stosamkrila.exe
shell\\explore\\command=ludasambila\\stosamkrila.exe
shell\\open\\command=ludasambila\\stosamkrila.exe

Step 6

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