WORM_WCRY.A
Win32/Exploit.CVE-2017-0147.A (ESET-NOD32), Ransom:Win32/WannaCrypt (Microsoft), Ransom.Wannacry (Symantec)
Windows
Threat Type: Worm
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
This Worm executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.
TECHNICAL DETAILS
Arrival Details
This malware arrives via the following means:
Autostart Technique
This Worm registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\mssecsvc2.0
Type = "16"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\mssecsvc2.0
Start = "2"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\mssecsvc2.0
ErrorControl = "1"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\mssecsvc2.0
ImagePath = {initial malware file path} -m security
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\mssecsvc2.0
DisplayName = Microsoft Security Center (2.0) Service
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\mssecsvc2.0
ObjectName = LocalSystem
It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
services\mssecsvc2.0
It starts the following services:
- mssecsvc2.0
Dropping Routine
This Worm drops the following files:
- %Windows%\tasksche.exe ← detected as Ransom_WANA.A
It executes the dropped file. As a result, malicious routines of the dropped file are exhibited on the affected system.
NOTES:
It connects to http://www.iuqerfsodp9ifjaposdfjhgosurijfaewrwergwea.com. If the connection is successful, it will stop execution. Hence, it is used as a kill switch for the infection.
It scans the following to check for open port 445:
- Hosts on the Local Area Network
- randomly-generated IP address over the Internet
If it finds a host either on the LAN/Internet with open port 445, it will attempt to exploit MS17-010 vulnerability to drop and execute a copy of itself to the remote host.
It uses the following file path for its dropped copies on the remote hosts:
- %Windows%\mssecsvc.exe
It checks for the presence of the file %WINDOWS%\tasksche.exe. If the file exist, it will move the file to the following directory %WINDOWS%\qeriuwjhrf\tasksche.exe.
It executes %Windows%\tasksche.exe with /i parameter.
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
Remove the malware/grayware file dropped/downloaded by WORM_WCRY.A. (Note: Please skip this step if the threat(s) listed below have already been removed.)
Step 3
Restart in Safe Mode
Step 4
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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\services
- mssecsvc2.0
- mssecsvc2.0
Step 5
Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_WCRY.A. 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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