WORM_YAHLOVER.JH
Windows 2000, Windows XP, Windows Server 2003
![](/vinfo/imgFiles/legend.jpg)
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
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%\chrome9.exe
- %Windows%\chrome9.exe
(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.. %Windows% is the Windows folder, which is usually C:\Windows.)
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%\chrome9.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 chrome9.exe"
(Note: The default value data of the said registry entry is Explorer.exe.)
Other System Modifications
This worm adds the following registry keys:
HKEY_LOCAL_MACHINE\Software\Policies\
Microsoft\Internet Explorer\Control Panel
HKEY_CURRENT_USER\Software\Policies\
Microsoft\Internet Explorer\Control Panel
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\SearchScopes
HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Internet Explorer\SearchScopes
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Internet Explorer\Control Panel
HomePage = "1"
HKEY_CURRENT_USER\Software\Policies\
Microsoft\Internet Explorer\Control Panel
HomePage = "1"
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
RunOnceComplete = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
RunOnceComplete = "1"
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
RunOnceHasShown = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
RunOnceHasShown = "1"
HKEY_CURRENT_USER\Software\Microsoft\
Search Assistant
DefaultSearchURL = "http://www.{BLOCKED}l.co.uk/index.php?page=search/web&search="
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
WorkgroupCrawler\Shares
shared = "\New Folder.exe"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\SearchScopes
URL = "{random characters}"
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\SearchScopes
URL = "{random characters}"
It modifies the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
Default_Page_URL = "http://www.{BLOCKED}10.com"
(Note: The default value data of the said registry entry is http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
Default_Search_URL = "http://www.{BLOCKED}10.com"
(Note: The default value data of the said registry entry is http://www.microsoft.com/isapi/redir.dll?prd=ie&ar=iesearch.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
Search Page = "http://www.{BLOCKED}10.com"
(Note: The default value data of the said registry entry is http://www.microsoft.com/isapi/redir.dll?prd=ie&ar=iesearch.)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
Start Page = "http://www.{BLOCKED}10.com"
(Note: The default value data of the said registry entry is http://www.microsoft.com/isapi/redir.dll?prd={SUB_PRD}&clcid={SUB_CLSID}&pver={SUB_PVER}&ar=home.)
HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Start Page = "http://www.{BLOCKED}10.com"
(Note: The default value data of the said registry entry is http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome.)
Dropping Routine
This worm drops the following files:
- %Desktop%\Search.lnk
- %Favorites%\Sioril.lnk
- %User Startup%\Search bar.lnk
- %User Profile%\My Documents\Search bar.lnk
- %User Profile%\Quick Launch\Search.lnk
- d:\New Folder.exe
- d:\chrome9.exe
(Note: %Desktop% is the current user's desktop, which is usually C:\Documents and Settings\{User Name}\Desktop on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\Desktop on Windows Vista and 7.. %Favorites% is the current user's Favorites folder, which is usually C:\Documents and Settings\{user name}\Favorites on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\Favorites on Windows Vista and 7.. %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.)
This report is generated via an automated analysis system.
SOLUTION
Step 1
Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.
Step 2
Identify and delete files detected as WORM_YAHLOVER.JH using either the Startup Disk or Recovery Console
Step 3
Delete this registry key
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\Policies\Microsoft\Internet Explorer
- Control Panel
- In HKEY_CURRENT_USER\Software\Policies\Microsoft\Internet Explorer
- Control Panel
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer
- SearchScopes
- In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Internet Explorer
- SearchScopes
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\Run
- Yahoo Messengger = "%System%\chrome9.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Internet Explorer\Control Panel
- HomePage = "1"
- In HKEY_CURRENT_USER\Software\Policies\Microsoft\Internet Explorer\Control Panel
- HomePage = "1"
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
- RunOnceComplete = "1"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
- RunOnceComplete = "1"
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
- RunOnceHasShown = "1"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
- RunOnceHasShown = "1"
- In HKEY_CURRENT_USER\Software\Microsoft\Search Assistant
- DefaultSearchURL = "http://www.{BLOCKED}l.co.uk/index.php?page=search/web&search="
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\WorkgroupCrawler\Shares
- shared = "\New Folder.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\SearchScopes
- URL = "{random characters}"
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\SearchScopes
- URL = "{random characters}"
Step 5
Restore these modified registry values
Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
- From: Default_Page_URL = "http://www.{BLOCKED}10.com"
To: Default_Page_URL = ""http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome""
- From: Default_Page_URL = "http://www.{BLOCKED}10.com"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
- From: Default_Search_URL = "http://www.{BLOCKED}10.com"
To: Default_Search_URL = ""http://www.microsoft.com/isapi/redir.dll?prd=ie&ar=iesearch""
- From: Default_Search_URL = "http://www.{BLOCKED}10.com"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
- From: Search Page = "http://www.{BLOCKED}10.com"
To: Search Page = ""http://www.microsoft.com/isapi/redir.dll?prd=ie&ar=iesearch""
- From: Search Page = "http://www.{BLOCKED}10.com"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
- From: Start Page = "http://www.{BLOCKED}10.com"
To: Start Page = ""http://www.microsoft.com/isapi/redir.dll?prd={SUB_PRD}&clcid={SUB_CLSID}&pver={SUB_PVER}&ar=home""
- From: Start Page = "http://www.{BLOCKED}10.com"
- In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
- From: Start Page = "http://www.{BLOCKED}10.com"
To: Start Page = ""http://www.microsoft.com/isapi/redir.dll?prd=ie&pver=6&ar=msnhome""
- From: Start Page = "http://www.{BLOCKED}10.com"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- From: Shell = "Explorer.exe chrome9.exe"
To: Shell = ""Explorer.exe""
- From: Shell = "Explorer.exe chrome9.exe"
Step 6
Search and delete these components
- %Desktop%\Search.lnk
- %Favorites%\Sioril.lnk
- %User Startup%\Search bar.lnk
- %User Profile%\My Documents\Search bar.lnk
- %User Profile%\Quick Launch\Search.lnk
- d:\New Folder.exe
- d:\chrome9.exe
Step 7
Scan your computer with your Trend Micro product to delete files detected as WORM_YAHLOVER.JH. 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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