Ransom.Win32.RYUK.THDBEAI
Trojan-Ransom.Win32.Encoder.aca(Kaspersky); Trojan:Win32/Occamy.B!bit (Microsoft)
Windows
Threat Type: Ransomware
Destructiveness: No
Encrypted: No
In the wild: Yes
OVERVIEW
Downloaded from the Internet
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.
It drops files as ransom note.
TECHNICAL DETAILS
122,368 bytes
EXE
Yes
09 May 2019
Connects to URLs/IPs, Encrypts files, Displays message/message boxes
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:
- %Public%\sys
(Note: %Public% is the folder that serves as a repository of files or folders common to all users, which is usually C:\Users\Public in Windows Vista, 7, and 8.)
It adds the following processes:
- %system%\cmd.exe /c reg add hkey_current_user\software\microsot\windows\currentversion\run /v svchos /t reg_sz /d {malware path and file name} /f
It adds the following mutexes to ensure that only one of its copies runs at any one time:
- FakeMutex
Autostart Technique
This Ransomware adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
svchos = "{malware path and file name}.exe"
Other Details
This Ransomware does the following:
- It only encrypts Fixed Drives
- Checks for all running processes and creates a remote thread to all running processes except the following:
- {Malware File Name}.exe
- csrss.exe
- explorer.exe
- lsaas.exe
- Avoids encrypting the following file extensions:
- dll
- DLL
- lnk
- LNK
- hrmlog
- HRMLOG
- ini
- INI
- exe
- EXE
Ransomware Routine
This Ransomware avoids encrypting files with the following strings in their file path:
- Windows
- AhnLab
- Chrome
- Mozilla
- $Recycle.Bin
- WINDOWS
It drops the following file(s) as ransom note:
- {Encrypted Directory}\RyukReadMe.txt
It leaves text files that serve as ransom notes containing the following text:
SOLUTION
9.850
14.946.06
18 Apr 2019
14.947.00
19 Apr 2019
Step 1
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 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
- svchos = "{Malware path and name}.exe"
- svchos = "{Malware path and name}.exe"
Step 5
Search and delete these files
- %Public%\sys
- {Encrypted Directory}\RyukReadMe.txt
Step 6
Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom.Win32.RYUK.THDBEAI. 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 7
Restore encrypted files from backup.
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