PE_WINDEX.C-O
PWS:Win32/Bzub (Microsoft), Mal/Buzb-A (SOPHOS_LITE)
Windows
Threat Type: File infector
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This File infector arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.
It deletes itself after execution.
TECHNICAL DETAILS
Arrival Details
This File infector 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 File infector drops the following copies of itself into the affected system and executes them:
- %Application Data%\Microsoft\Messenger\Extension\WdExt.exe
(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)
It creates the following folders:
- %Application Data%\Temp
(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)
Autostart Technique
This File infector adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Windows Defender Extension = "%Application Data%\Microsoft\Defender\launch.exe"
Other System Modifications
This File infector adds the following registry keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{GUID}
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{GUID}
StubPath = "%System%\mscaps.exe" /s /n /i:U shell32.dll
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{GUID}
ComponentID = DirectShow
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{GUID}
Version = 1,125,2406,1
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{GUID}
Locale = *
File Infection
This File infector infects the following files:
- .exe files in shared folders and removable drives
Dropping Routine
This File infector drops the following files:
- %Application Data%\Temp\mydll.dll
- %Application Data%\Temp\{Username}{number}.bat
- %%Application Data%\Microsoft\Identities\{Username}\arc.dll
- %Application Data%\Microsoft\Windows\Addins\att.dll
- %Application Data%\Microsoft\Common\Shared\dis.dll
- %Application Data%\Microsoft\Shared\Modules\fil.dll
- %Application Data%\Microsoft\Repairs\sha.dll
- %Application Data%\Microsoft\Caches\Files\usd.dll
- %Application Data%\Microsoft\Defender\launch.exe
- %System%\mscaps.exe
- %System%\wtime32.dll
(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)
Other Details
This File infector connects to the following URL(s) to check for an Internet connection:
- windowsupdate.microsoft.com
- update.microsoft.com
It connects to the following possibly malicious URL:
- a.gwas.{BLOCKED}l.sh
- {BLOCKED}krCmkrZgqoLAYHBgbGJ6hHhsbmZw.g.s
- a-gwas-01.{BLOCKED}p.net
- a-gwas-01.{BLOCKED}s.org
It deletes itself after execution.
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
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
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
- Windows Defender Extension = "%Application Data%\Microsoft\Defender\launch.exe"
- Windows Defender Extension = "%Application Data%\Microsoft\Defender\launch.exe"
Step 5
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.
- HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{GUID}
Step 6
Search and delete this folder
- %Application Data%\Temp
Step 7
Search and delete these files
- %Application Data%\Microsoft\Messenger\Extension\WdExt.exe
- %%Application Data%\Microsoft\Identities\{Username}\arc.dll
- %Application Data%\Microsoft\Windows\Addins\att.dll
- %Application Data%\Microsoft\Common\Shared\dis.dll
- %Application Data%\Microsoft\Shared\Modules\fil.dll
- %Application Data%\Microsoft\Repairs\sha.dll
- %Application Data%\Microsoft\Caches\Files\usd.dll
- %Application Data%\Microsoft\Defender\launch.exe
- %System%\mscaps.exe
- %System%\wtime32.dll
Step 8
Restart in normal mode and scan your computer with your Trend Micro product for files detected as PE_WINDEX.C-O. 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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