Ransom.Win32.MAUICRYPT.YACC5
W32/MAUICRYPT.YACC5!tr.ransom (FORTINET)
Windows
Threat Type: Ransomware
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
This Ransomware 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 Ransomware 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 Ransomware drops the following files:
- {Malware Path}\maui.evd → RSA private key generated at runtime
- {Malware Path}\maui.key → RSA public key generated at runtime
- {Malware Path}\maui.log → Log file containing output console output from execution
- %User Temp%\dgod.bat → Used to delete itself
(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)
It adds the following processes:
- %System%\cmd.exe /c start /b "" cmd /c "%User Temp%\dgod.bat"
- ping localhost -n 1
- del /f /q "{Malware Path}\{Malware Filename}"
- TASKKILL /IM "{Malware Path}\{Malware Filename}"
(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000(32-bit), XP, and Server 2003(32-bit), or C:\Users\{user name}\AppData\Local\Temp on Windows Vista, 7, 8, 8.1, 2008(64-bit), 2012(64-bit) and 10(64-bit).)
Other Details
This Ransomware does the following:
- It does not rename encrypted files.
- It does not drop a ransom note.
- It requires to be executed with an argument {target path} to proceed to encryption.
It accepts the following parameters:
- -p {Path} → Set log directory
- -t {n} → Set thread count
- -x → Delete itself
- {target path} → Encrypts only specified path
SOLUTION
Step 1
Trend Micro Predictive Machine Learning detects and blocks malware at the first sign of its existence, before it executes on your system. When enabled, your Trend Micro product detects this malware under the following machine learning name:
- TROJ.Win32.TRX.XXPE50FFF058
Step 2
Before doing any scans, Windows 7, Windows 8, Windows 8.1, and Windows 10 users must disable System Restore to allow full scanning of their computers.
Step 3
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 4
Identify and terminate files detected as Ransom.Win32.MAUICRYPT.YACC5
- Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
- If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
- If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.
Step 5
Search and delete this file
- {Malware Path}\maui.evd
- {Malware Path}\maui.key
- {Malware Path}\maui.log
- %User Temp%\dgod.bat
Step 6
Scan your computer with your Trend Micro product to delete files detected as Ransom.Win32.MAUICRYPT.YACC5. 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 the following Trend Micro Support pages for more information:
Step 7
Restore encrypted files from backup.
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