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WORM_PALEVO.SMGA

October 09, 2012
 Analysis by: Christopher Daniel So
 ALIASES:

Trojan:Win32/Rimecud.A (Microsoft), Trojan.Win32.Pincav.ajmb (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 flashdrives


This worm arrives via 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 connects to certain websites to send and receive information. However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

Varies

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

09 Dec 2010

Payload:

Drops files, Creates files, Connects to URLs/IPs

Arrival Details

This worm arrives via removable drives.

Installation

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

  • %User Profile%\Application Data\vfbu.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 adds the following mutexes to ensure that only one of its copies runs at any one time:

  • K/Fz+56

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\CurrentVersion\Winlogon
Taskman = "%User Profile%\Application Data\vfbu.exe"

Other System Modifications

This worm adds the following registry keys:

HKEY_CLASSES_ROOT\CLSID\{ABF9E1AD-556E-9CDD-C65E-7DC2090FC2D7}

HKEY_CURRENT_USER\Software\Licenses

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
RFC1156Agent

It adds the following registry entries:

HKEY_CLASSES_ROOT\CLSID\{ABF9E1AD-556E-9CDD-C65E-7DC2090FC2D7}\
InProcServer32
(Default) = "%SystemRoot%\system32\dsuiext.dll"

HKEY_CLASSES_ROOT\CLSID\{ABF9E1AD-556E-9CDD-C65E-7DC2090FC2D7}\
InProcServer32
ThreadingModel = "Apartment"

HKEY_CLASSES_ROOT\CLSID\{ABF9E1AD-556E-9CDD-C65E-7DC2090FC2D7}\
ShellEx\MayChangeDefaultMenu
(Default) = "1"

HKEY_CURRENT_USER\Software\Licenses
{K7C0DB872A3F777C0} = "{random numbers}"

HKEY_CURRENT_USER\Software\Licenses
{I5BF672D06FBF693E} = "{random numbers}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
RFC1156Agent\CurrentVersion\Parameters
TrapPollTimeMilliSecs = "3a98"

Propagation

This worm drops the following copy(ies) of itself in all removable drives:

  • {removable drive letter}:\U3ROM\system32.exe

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:

;2438uxZysrgOsS3oPi9WHNrYpmhdh la
[autorun]
open=U3ROM/system32.exe
;kjcxziuyyuc^^dj[
icon=U3ROM/default.ico
;jdkaZysrgOsS3oPi9WHNrYpmkjfjkasdfh
action=Open
;1s0PSq7YZysrgOsS3oPi9WHNrYpmdP5v8736B4yu4d2I2308cT\8
shell\open\command=U3ROM/system32.exe
shell\explore\command=U3ROM/system32.exe
useautoplay=1
:GOTO NUL
;]2y3ZysrgOsS3oPi9WHNrYpm\lV=66q8

Other Details

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

  • {BLOCKED}dates2000.com
  • {BLOCKED}windows.net
  • {BLOCKED}ureserv.com
  • {BLOCKED}servis.in
  • {BLOCKED}cureupdate.com

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

NOTES:
It creates the following folder in all removable drives:

  • {removable drive letter}:\U3ROM
It drops the following file in all removable drives:
  • {removable drive letter}:\U3ROM\default.ico
The dropped AUTORUN.INF file is detected as TROJ_OTORUN.GK.

  SOLUTION

Minimum Scan Engine:

8.900

FIRST VSAPI PATTERN FILE:

7.702.08

FIRST VSAPI PATTERN DATE:

15 Dec 2010

VSAPI OPR PATTERN File:

7.703.00

VSAPI OPR PATTERN Date:

15 Dec 2010

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

Remove malware files dropped/downloaded by WORM_PALEVO.SMGA

Step 3

Identify and delete files detected as WORM_PALEVO.SMGA using either the Startup Disk or Recovery Console

[ 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\CurrentVersion\Winlogon
    • Taskman = "%User Profile%\Application Data\vfbu.exe"

Step 5

Delete this registry key

[ 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_CLASSES_ROOT\CLSID
    • {ABF9E1AD-556E-9CDD-C65E-7DC2090FC2D7}
  • In HKEY_CURRENT_USER\Software
    • Licenses
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft
    • RFC1156Agent

Step 6

Search and delete this folder

[ 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.
  • {removable drive letter}:\U3ROM

Step 7

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

[ Learn More ]
;2438uxZysrgOsS3oPi9WHNrYpmhdh la
[autorun]
open=U3ROM/system32.exe 
;kjcxziuyyuc^^dj[
icon=U3ROM/default.ico
;jdkaZysrgOsS3oPi9WHNrYpmkjfjkasdfh
action=Open 
;1s0PSq7YZysrgOsS3oPi9WHNrYpmdP5v8736B4yu4d2I2308cT\8
shell\open\command=U3ROM/system32.exe
shell\explore\command=U3ROM/system32.exe
useautoplay=1
:GOTO NUL
;]2y3ZysrgOsS3oPi9WHNrYpm\lV=66q8

Step 8

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