WORM_LEGMIR.GT
PWS:Win32/Lmir (Microsoft), PWS-LegMir (McAfee)
Windows 2000, Windows XP, Windows Server 2003
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.
It employs registry shell spawning by adding certain registry entries. This allows this malware to execute even when other applications are opened.
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
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:
- %Program Files%\Common Files\iexplore.pif
- %Program Files%\Internet Explorer\iexplore.com
- %System%\command.pif
- %System%\dxdiag.com
- %System%\finder.com
- %System%\MSCONFIG.COM
- %System%\regedit.com
- %System%\rundll32.com
- %Windows%\1.com
- %Windows%\Debug\DebugProgram.exe
- %Windows%\ExERoute.exe
- %Windows%\explorer.com
- %Windows%\finder.com
- D:\pagefile.pif
- %Windows%\services.exe
Autostart Technique
This worm creates the following registry entries to enable automatic execution of dropped component at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Torjan Program = "%Windows%\services.exe"
It employs registry shell spawning to ensure its execution when certain file types are accessed by adding the following entries:
HKEY_CLASSES_ROOT\winfiles\Shell\
Open\Command
@ = "%Windows%\ExeRoute.exe "%1" %*"
HKEY_LOCAL_MACHINE\SOFTWARE\Clients\
StartMenuInternet\iexplore.pif\shell
@ = "%Program Files%\Common Files\iexplore.pif"
Other System Modifications
This worm adds the following registry keys:
HKEY_CURRENT_USER\Software\VB and VBA Program Settings
HKEY_CLASSES_ROOT\winfiles
HKEY_LOCAL_MACHINE\SOFTWARE\Clients\
StartMenuInternet\iexplore.pif\shell
It adds the following registry entries:
HKEY_CURRENT_USER\Software\Internet Explorer\
Main
Check_Associations = "No"
It modifies the following registry entries:
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
Applications\iexplore.exe\shell\
open\command
@ = ""%Program Files%\Internet Explorer\iexplore.com" %1"
(Note: The default value data of the said registry entry is "%Program Files%\Internet Explorer\iexplore.exe" %1.)
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
.lnk\ShellNew
Command = "%System%\rundll32.com appwiz.cpl,NewLinkHere %1"
(Note: The default value data of the said registry entry is %System%\rundll32.exe appwiz.cpl,NewLinkHere %1.)
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
cplfile\shell\cplopen\
command
@ = "rundll32.com shell32.dll,Control_RunDLL "%1",%*"
(Note: The default value data of the said registry entry is rundll32.exe shell32.dll,Control_RunDLL "%1",%*.)
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
CLSID\{871C5380-42A0-1069-A2EA-08002B30309D}\shell\
OpenHomePage\Command
@ = "%Program Files%\Internet Explorer\iexplore.com"
(Note: The default value data of the said registry entry is %Program Files%\Internet Explorer\iexplore.exe.)
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
Drive\shell\find\
command
@ = "SystemRoot%\explorer.com"
(Note: The default value data of the said registry entry is SystemRoot%\explorer.exe.)
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
dunfile\shell\open\
command
@ = "%System%\rundll32.com NETSHELL.DLL,InvokeDunFile %1"
(Note: The default value data of the said registry entry is %System%\rundll32.exe NETSHELL.DLL,InvokeDunFile %1.)
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
ftp\shell\open\
command
@ = ""%Program Files%\Internet Explorer\iexplore.com" %1"
(Note: The default value data of the said registry entry is "%Program Files%\Internet Explorer\iexplore.exe" %1.)
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
htmlfile\shell\open\
command
@ = ""%Program Files%\Internet Explorer\iexplore.com" -nohome"
(Note: The default value data of the said registry entry is "%Program Files%\Internet Explorer\iexplore.exe" -nohome.)
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
htmlfile\shell\opennew\
command
@ = ""%Program Files%\Internet Explorer\iexplore.com" %1"
(Note: The default value data of the said registry entry is "%Program Files%\Internet Explorer\iexplore.exe" %1.)
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
HTTP\shell\open\
command
@ = ""%Program Files%\Internet Explorer\iexplore.com" -nohome"
(Note: The default value data of the said registry entry is "%Program Files%\Internet Explorer\iexplore.exe" -nohome.)
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
inffile\shell\Install\
command
@ = "%System%\rundll32.com setupapi,InstallHinfSection DefaultInstall 132 %1"
(Note: The default value data of the said registry entry is %System%\rundll32.exe setupapi,InstallHinfSection DefaultInstall 132 %1 .)
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
InternetShortcut\shell\open\
command
@ = "finder.com shdocvw.dll,OpenURL %l"
(Note: The default value data of the said registry entry is rundll32.exe shdocvw.dll,OpenURL %l.)
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
scrfile\shell\install\
command
@ = "finder.com desk.cpl,InstallScreenSaver %l"
(Note: The default value data of the said registry entry is rundll32.exe desk.cpl,InstallScreenSaver %l.)
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
scriptletfile\Shell\Generate Typelib\
command
@ = ""%System%\finder.com" %System%\scrobj.dll,GenerateTypeLib "%1""
(Note: The default value data of the said registry entry is "%System%\rundl32.dll" %System%\scrobj.dll,GenerateTypeLib "%1".)
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
telnet\shell\open\
command
@ = "finder.com url.dll,TelnetProtocolHandler %l"
(Note: The default value data of the said registry entry is rundll32.exe url.dll,TelnetProtocolHandler %l.)
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
.exe
@ = "winfiles"
(Note: The default value data of the said registry entry is exefile.)
HKEY_CLASSES_ROOT\SOFTWARE\Classes\
.bfc\ShellNew
Command = "%System%\rundll32.com %System%\syncui.dll,Briefcase_Create %2!d! %1"
(Note: The default value data of the said registry entry is %System%\rundll32.exe %System%\syncui.dll,Briefcase_Create %2!d! %1.)
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Unknown\shell\openas\
command
@ = "%System%\finder.com %System%\shell32.dll,OpenAs_RunDLL %1"
(Note: The default value data of the said registry entry is %System%\rundll32.exe %System%\shell32.dll,OpenAs_RunDLL %1 .)
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "Explorer.exe 1"
(Note: The default value data of the said registry entry is Explorer.exe.)
Propagation
This worm 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=D:\pagefile.pif
Other Details
This worm connects to the following possibly malicious URL:
- http://account.{BLOCKED}t.com.cn/UPD/Information.asp?UID={value}&UID88={value}
SOLUTION
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
Restart in Safe Mode
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_CLASSES_ROOT
- winfiles
- winfiles
- In HKEY_LOCAL_MACHINE\SOFTWARE\Clients\StartMenuInternet\iexplore.pif
- shell
- shell
- In HKEY_CURRENT_USER\Software
- VB and VBA Program Settings
- VB and VBA Program Settings
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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- Torjan Program = "%Windows%\services.exe"
- Torjan Program = "%Windows%\services.exe"
- In HKEY_CURRENT_USER\Software\Internet Explorer\Main
- Check_Associations = "No"
- Check_Associations = "No"
Step 5
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_CLASSES_ROOT\SOFTWARE\Classes\Applications\iexplore.exe\shell\open\command
- From: @ = ""%Program Files%\Internet Explorer\iexplore.com" %1"
To: @ = ""%Program Files%\Internet Explorer\iexplore.exe" %1"
- From: @ = ""%Program Files%\Internet Explorer\iexplore.com" %1"
- In HKEY_CLASSES_ROOT\SOFTWARE\Classes\.lnk\ShellNew
- From: Command = "%System%\rundll32.com appwiz.cpl,NewLinkHere %1"
To: Command = "%System%\rundll32.exe appwiz.cpl,NewLinkHere %1"
- From: Command = "%System%\rundll32.com appwiz.cpl,NewLinkHere %1"
- In HKEY_CLASSES_ROOT\SOFTWARE\Classes\cplfile\shell\cplopen\command
- From: @ = "rundll32.com shell32.dll,Control_RunDLL "%1",%*"
To: @ = "rundll32.exe shell32.dll,Control_RunDLL "%1",%*"
- From: @ = "rundll32.com shell32.dll,Control_RunDLL "%1",%*"
- In HKEY_CLASSES_ROOT\SOFTWARE\Classes\CLSID\{871C5380-42A0-1069-A2EA-08002B30309D}\shell\OpenHomePage\Command
- From: @ = "%Program Files%\Internet Explorer\iexplore.com"
To: @ = "%Program Files%\Internet Explorer\iexplore.exe"
- From: @ = "%Program Files%\Internet Explorer\iexplore.com"
- In HKEY_CLASSES_ROOT\SOFTWARE\Classes\Drive\shell\find\command
- From: @ = "SystemRoot%\explorer.com"
To: @ = "SystemRoot%\explorer.exe"
- From: @ = "SystemRoot%\explorer.com"
- In HKEY_CLASSES_ROOT\SOFTWARE\Classes\dunfile\shell\open\command
- From: @ = "%System%\rundll32.com NETSHELL.DLL,InvokeDunFile %1"
To: @ = "%System%\rundll32.exe NETSHELL.DLL,InvokeDunFile %1"
- From: @ = "%System%\rundll32.com NETSHELL.DLL,InvokeDunFile %1"
- In HKEY_CLASSES_ROOT\SOFTWARE\Classes\ftp\shell\open\command
- From: @ = ""%Program Files%\Internet Explorer\iexplore.com" %1"
To: @ = ""%Program Files%\Internet Explorer\iexplore.exe" %1"
- From: @ = ""%Program Files%\Internet Explorer\iexplore.com" %1"
- In HKEY_CLASSES_ROOT\SOFTWARE\Classes\htmlfile\shell\open\command
- From: @ = ""%Program Files%\Internet Explorer\iexplore.com" -nohome"
To: @ = ""%Program Files%\Internet Explorer\iexplore.exe" -nohome"
- From: @ = ""%Program Files%\Internet Explorer\iexplore.com" -nohome"
- In HKEY_CLASSES_ROOT\SOFTWARE\Classes\htmlfile\shell\opennew\command
- From: @ = ""%Program Files%\Internet Explorer\iexplore.com" %1"
To: @ = ""%Program Files%\Internet Explorer\iexplore.exe" %1"
- From: @ = ""%Program Files%\Internet Explorer\iexplore.com" %1"
- In HKEY_CLASSES_ROOT\SOFTWARE\Classes\HTTP\shell\open\command
- From: @ = ""%Program Files%\Internet Explorer\iexplore.com" -nohome"
To: @ = ""%Program Files%\Internet Explorer\iexplore.exe" -nohome"
- From: @ = ""%Program Files%\Internet Explorer\iexplore.com" -nohome"
- In HKEY_CLASSES_ROOT\SOFTWARE\Classes\inffile\shell\Install\command
- From: @ = "%System%\rundll32.com setupapi,InstallHinfSection DefaultInstall 132 %1"
To: @ = "%System%\rundll32.exe setupapi,InstallHinfSection DefaultInstall 132 %1"
- From: @ = "%System%\rundll32.com setupapi,InstallHinfSection DefaultInstall 132 %1"
- In HKEY_CLASSES_ROOT\SOFTWARE\Classes\InternetShortcut\shell\open\command
- From: @ = "finder.com shdocvw.dll,OpenURL %l"
To: @ = "rundll32.exe shdocvw.dll,OpenURL %l"
- From: @ = "finder.com shdocvw.dll,OpenURL %l"
- In HKEY_CLASSES_ROOT\SOFTWARE\Classes\scrfile\shell\install\command
- From: @ = "finder.com desk.cpl,InstallScreenSaver %l"
To: @ = "rundll32.exe desk.cpl,InstallScreenSaver %l"
- From: @ = "finder.com desk.cpl,InstallScreenSaver %l"
- In HKEY_CLASSES_ROOT\SOFTWARE\Classes\scriptletfile\Shell\Generate Typelib\command
- From: @ = ""%System%\finder.com" %System%\scrobj.dll,GenerateTypeLib "%1""
To: @ = ""%System%\rundll32.exe" %System%\scrobj.dll,GenerateTypeLib "%1""
- From: @ = ""%System%\finder.com" %System%\scrobj.dll,GenerateTypeLib "%1""
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\telnet\shell\open\command
- From: @ = "finder.com url.dll,TelnetProtocolHandler %l"
To: @ = "rundll32.exe url.dll,TelnetProtocolHandler %l"
- From: @ = "finder.com url.dll,TelnetProtocolHandler %l"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Unknown\shell\openas\command
- From: @ = "%System%\finder.com %System%\shell32.dll,OpenAs_RunDLL %1"
To: @ = "%System%\rundll32.exe %System%\shell32.dll,OpenAs_RunDLL %1"
- From: @ = "%System%\finder.com %System%\shell32.dll,OpenAs_RunDLL %1"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- From: Shell = "Explorer.exe 1"
To: Shell = "Explorer.exe"
- From: Shell = "Explorer.exe 1"
- In HKEY_CLASSES_ROOT\SOFTWARE\Classes\.exe
- From: @ = "winfiles"
To: @ = "exefile"
- From: @ = "winfiles"
- In HKEY_CLASSES_ROOT\SOFTWARE\Classes\.bfc\ShellNew
- From: Command = "%System%\rundll32.com %System%\syncui.dll,Briefcase_Create %2!d! %1"
To: Command = "%System%\rundll32.exe %System%\syncui.dll,Briefcase_Create %2!d! %1"
- From: Command = "%System%\rundll32.com %System%\syncui.dll,Briefcase_Create %2!d! %1"
Step 6
Search and delete AUTORUN.INF files created by WORM_LEGMIR.GT that contain these strings
OPEN=D:\pagefile.pif
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_LEGMIR.GT. 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.
Step 8
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.
RESTOREStep 9
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.
RESTOREStep 10
Restore this modified registry value
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.
RESTOREDid this description help? Tell us how we did.