WORM_OTORUN.XXSK
Virus:Win32/Capsfin.A (MICROSOFT), W32/Madang.C (FORTINET)
Windows

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 disables Task Manager, Registry Editor, and Folder Options. It modifies registry entries to disable the Windows Firewall settings. This action allows this malware to perform its routines without being deteted by the Windows Firewall. It modifies certain registry entries to hide file extensions.
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
241,664 bytes
EXE
01 Aug 2018
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:
- {drive letter}:\SYS\AAR.exe
- {drive letter}:\SYS\SYS.exe
- %System Root%\Documents and Settings\Administrator\{malware name}.exe
- %System%\restore\Thole.exe
- %System%\com\THole.exe
- %Windows%\{malware name}.exe
- %System%\inf\svchost.exe
(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)
Autostart Technique
This Worm adds the following registry entries to enable its automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
NTD = %System%\Com\THole.exe
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
NT = %System Root%\Documents and Settings\Administrator\{malware name}.exe
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\RunOnce
Startup Scan = %Windows%\{malware name}.exe/check
It adds and runs the following services:
- eventchk
Other System Modifications
This Worm modifies the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\AeLookupSvc
Type = 16
(Note: The default value data of the said registry entry is 20.)
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\Winmgmt
Type = 16
(Note: The default value data of the said registry entry is 20.)
It creates the following registry entry(ies) to disable Task Manager, Registry Tools and Folder Options:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableRegistryTools = 0
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = 1
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\SuperHidden
CheckedValue = 1
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\SuperHidden
UncheckedValue = 0
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\
NOHIDDEN
DefaultValue = 1
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\
SHOWALL
CheckedValue = 1
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\Hidden\
SHOWALL
DefaultValue = 2
It modifies the following registry entries to disable the Windows Firewall settings:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
list\%System%\inf
svchost.exe = %System%\inf\svchost.exe:*:Enabled:@xpsp2res.dll,-22001
It modifies the following registry entries to hide file extensions:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\HideFileExt
UncheckedValue = 1
Propagation
This Worm searches for folders in all physical and removable drives then drops copies of itself inside the folder as {folder name}.EXE.
It drops an AUTORUN.INF file to automatically execute the copies it drops when a user accesses the drives of an affected system.
SOLUTION
9.850
14.412.06
30 Jul 2018
14.413.00
31 Jul 2018
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
Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.
Step 3
Restart in Safe Mode
Step 4
Enable Registry Editor, Task Manager, and Folder options
Step 5
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 NT\CurrentVersion\Winlogon
- NTD = %System%\Com\THole.exe
- NTD = %System%\Com\THole.exe
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- NT = %System Root%\Documents and Settings\Administrator\{malware name}.exe
- NT = %System Root%\Documents and Settings\Administrator\{malware name}.exe
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce
- Startup Scan = %System Root%\WINDOWS\{malware name}.exe/check
- Startup Scan = %System Root%\WINDOWS\{malware name}.exe/check
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\list\%System%\inf
- svchost.exe = %System%\inf\svchost.exe:*:Enabled:@xpsp2res.dll,-22001
- svchost.exe = %System%\inf\svchost.exe:*:Enabled:@xpsp2res.dll,-22001
Step 6
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\SYSTEM\ControlSet001\services\AeLookupSvc
- From: Type = 16
To: Type = 20
- From: Type = 16
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services\Winmgmt
- From: Type = 16
To: Type = 20
- From: Type = 16
Step 7
Search and delete these files
- {drive letter}:\SYS\AAR.exe
- {drive letter}:\SYS\SYS.exe
- %System%\restore\Thole.exe
- %System%\com\THole.exe
- %Windows%\{malware name}.exe
- %System%\inf\svchost.exe
- %System Root%\Documents and Settings\Administrator\{malware name}.exe
Step 8
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_OTORUN.XXSK. 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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