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WORM_YAHLOVER.AE

October 12, 2012
 ALIASES:

Worm:Win32/YahLover.C (Microsoft); :W32/Yahlover.worm.gen.k (McAfee); ARC:Embedded, [script.au3]:Worm.Win32.AutoIt.sp, [script.au3]:Worm.Win32.AutoIt.sp (Kaspersky); Trojan.Win32.AutoIt.gen.4 (v) (Sunbelt); Trojan.Downloader.JMGF (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


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.

  TECHNICAL DETAILS

File Size:

680,960 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

05 Apr 2012

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:

  • %System%\scvhost.exe
  • %Windows%\scvhost.exe

(Note: %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.. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

Autostart Technique

This worm adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Yahoo Messengger = "%System%\scvhost.exe"

It modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "Explorer.exe scvhost.exe"

(Note: The default value data of the said registry entry is Explorer.exe.)

Other System Modifications

This worm adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Schedule
AtTaskMaxHours = "0"

Other Details

This worm connects to the following possibly malicious URL:

  • http://advgoogle.{BLOCKED}h.com/setting.nql
  • http://advgoogle.{BLOCKED}h.com/setting.xls

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

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_YAHLOVER.AE 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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Yahoo Messengger = "%System%\scvhost.exe"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Schedule
    • AtTaskMaxHours = "0"

Step 4

Restore this modified 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
    • From: Shell = "Explorer.exe scvhost.exe"
      To: Shell = ""Explorer.exe""

Step 5

Scan your computer with your Trend Micro product to delete files detected as WORM_YAHLOVER.AE. 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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