WORM_YAHLOVER.C
Worm:Win32/YahLover.C (Microsoft), W32/Yahlover.worm.gen.k (McAfee), W32.Imaut (Symantec), W32/Sohanat.DD.worm (Panda)
Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)
Threat Type: Worm
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This worm 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 an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.
TECHNICAL DETAILS
660,480 bytes
EXE
Yes
15 Nov 2012
Arrival Details
This worm 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:
- %Windows%\scvhost.exe
- %System%\scvhost.exe
(Note: %Windows% is the Windows folder, which is usually C:\Windows.. %System% is the Windows system folder, which is usually C:\Windows\System32.)
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 drops the following files:
- %System%\autorun.ini
(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)
Other System Modifications
This worm adds the following registry entries:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings
GlobalUserOffline = "0"
It modifies the following registry entries:
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".)
Propagation
This worm drops the following copy(ies) of itself in all removable drives:
- {drive letter}:\new folder.exe
- {drive letter}:\scvhost.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:
[Autorun]
Open=scvhost.exe
Shellexe cute=scvhost.exe
Shell\Open\command=scvhost.exe
Shell=Open
Other Details
This worm connects to the following possibly malicious URL:
- advgoogle.{BLOCKED}h.com
SOLUTION
9.300
9.528.02
15 Nov 2012
9.529.00
16 Nov 2012
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.C using the Recovery Console
Step 3
Restore this modified registry value
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"
- From: Shell = "Explorer.exe scvhost.exe"
Step 4
Delete this registry value
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\Internet Settings
- GlobalUserOffline = "0"
- GlobalUserOffline = "0"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- Yahoo Messengger = "%System%\scvhost.exe"
- Yahoo Messengger = "%System%\scvhost.exe"
Step 5
Search and delete this file
- %System%\autorun.ini
Step 6
Search and delete AUTORUN.INF files created by WORM_YAHLOVER.C that contain these strings
[Autorun]
Open=scvhost.exe
Shellexe cute=scvhost.exe
Shell\Open\command=scvhost.exe
Shell=Open
Step 7
Scan your computer with your Trend Micro product to delete files detected as WORM_YAHLOVER.C 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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