RANSOM_CRYPTESLA.CBQ2N
Ransom:Win32/Tescrypt.H (Microsoft)
Windows
Threat Type: Trojan
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
This Trojan 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 the initially executed copy of itself. It is capable of encrypting files in the affected system.
TECHNICAL DETAILS
Arrival Details
This Trojan 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 Trojan drops the following copies of itself into the affected system and executes them:
- %Windows%\{random filename}.exe
(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)
It drops the following files:
- %User Profile%\Documents\recover_file_{random letters}.txt
- %Desktop%\RECOVERY.HTM
- %Desktop%\RECOVERY.png
- %Desktop%\RECOVERY.TXT
- {Folders containg encrypted files}\Recovery+{random letters}.png
- {Folders containg encrypted files}\Recovery+{random letters}.txt
- {Folders containg encrypted files}\Recovery+{random letters}.html
(Note: %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %Desktop% is the desktop folder, where it usually is C:\Documents and Settings\{user name}\Desktop in Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\Desktop in 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 Trojan adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random} = "%System%\cmd.exe /c start "" "%Windows%\{random filename}.exe""
Other System Modifications
This Trojan adds the following registry keys:
HKEY_CURRENT_USER\Software\xxxsys
HKEY_CURRENT_USER\Software\{Installation ID}
It adds the following registry entries:
HKEY_CURRENT_USER\Software\{Installation ID}
data = {encryption information}
HKEY_CURRENT_USER\Software\xxxsys
ID = {Installation ID}
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
EnabledLinkConnections = "1"
Other Details
This Trojan connects to the following possibly malicious URL:
- http://{BLOCKED}de.co.kr/board/common/bsts.php
- http://{BLOCKED}group.com/plugins/bsts.php
- http://{BLOCKED}dmarketing101.net/docs/cache/bsts.php
- http://{BLOCKED}anph.com/wp-content/uploads/bsts.php
- http://{BLOCKED}inslow.com/csys.php
- http://{BLOCKED}dress.pl/wp-content/themes/sketch/csys.php
It deletes the initially executed copy of itself
It is capable of encrypting files in the affected system.
NOTES:
It appends the extension .mp3 to the file name of the encrypted files.
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
Scan your computer with your Trend Micro product and note files detected as RANSOM_CRYPTESLA.CBQ2N
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
- {random} = "%System%\cmd.exe /c start "" "%Windows%\{random filename}.exe""
- {random} = "%System%\cmd.exe /c start "" "%Windows%\{random filename}.exe""
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system
- EnableLinkedConnections = "1"
- EnableLinkedConnections = "1"
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.
- In HKEY_CURRENT_USER\Software
- xxxsys
- xxxsys
- In HKEY_CURRENT_USER\Software
- {Installation ID}
- {Installation ID}
Step 6
Search and delete this file
- %User Profile%\Documents\recover_file_{random letters}.txt
- %Desktop%\RECOVERY.HTM
- %Desktop%\RECOVERY.png
- %Desktop%\RECOVERY.TXT
- Recovery+{random letters}.png
- Recovery+{random letters}.txt
- Recovery+{random letters}.html
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_CRYPTESLA.CBQ2N. 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 8
Restore encrypted files from backup.
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