RANSOM_CRYPTESLA.YYSIZ
Ransom.TeslaCrypt (MalwareBytes), Ransom:Win32/Tescrypt.A (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 modifies the Internet Explorer Zone Settings.
It deletes itself after execution.
TECHNICAL DETAILS
352,256 bytes
EXE
10 Dec 2015
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:
- %Application Data%\{5 random letters}acroic.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.)
Other System Modifications
This Trojan adds the following registry keys:
HKEY_CURRENT_USER\Software\zsys
HKEY_CURRENT_USER\Software\{installation ID}
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
System
EnabledLinkConnections = "1"
HKEY_CURRENT_USER\Software\{installation ID}
data = "{encryption information}"
HKEY_CURRENT_USER\Software\zsys
ID = "{installation ID}"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Acrndtd = "%Application Data%\{5 random letters}acroic.exe"
Web Browser Home Page and Search Page Modification
This Trojan modifies the Internet Explorer Zone Settings.
Dropping Routine
This Trojan drops the following files:
- %User Profile%\Documents\recover_file_{9 random letters}.txt
- %Desktop%\Howto_RESTORE_FILES.txt
- %Desktop%\Howto_RESTORE_FILES.html
- %Desktop%\Howto_RESTORE_FILES.bmp
(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.)
Other Details
This Trojan connects to the following URL(s) to get the affected system's IP address:
- http://myexternalip.com/raw
It connects to the following possibly malicious URL:
- http://{BLOCKED}n.{BLOCKED}io.pl/media/misc.php
- http://{BLOCKED}lbrass.no/media/misc.php
- http://{BLOCKED}yasphalt.com/media/misc.php
- http://{BLOCKED}tup.com/media/misc.php
- http://{BLOCKED}grandes.com/media/misc.php
- http://{BLOCKED}nacademy.com/media/misc.php
It opens the following files:
- dropped %Desktop%\Howto_RESTORE_FILES.txt
- dropped %Desktop%\Howto_RESTORE_FILES.html
- dropped %Desktop%\Howto_RESTORE_FILES.bmp
(Note: %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.)
It does the following:
- It is capable of encrypting files in the affected system, encrypted file names are appended with .vvv extension
- It drops how_recover+{3 random letters}.html and how_recover+{3 random letters}.txt to the folders where the files are encrypted
It deletes itself after execution.
SOLUTION
9.800
12.202.05
10 Dec 2015
12.203.00
11 Dec 2015
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 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
- zsys
- zsys
- In HKEY_CURRENT_USER\Software
- {installation ID}
- {installation ID}
Step 5
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
- Acrndtd = "%Application Data%\{5 random letters}acroic.exe"
- Acrndtd = "%Application Data%\{5 random letters}acroic.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
- EnabledLinkConnections = "1"
- EnabledLinkConnections = "1"
Step 6
Search and delete these files
- %User Profile%\Documents\recover_file_{9 random letters}.txt
- %Desktop%\Howto_RESTORE_FILES.txt
- %Desktop%\Howto_RESTORE_FILES.html
- %Desktop%\Howto_RESTORE_FILES.bmp
- how_recover+{3 random letters}.html
- how_recover+{3 random letters}.txt
Step 7
Reset Internet security settings
Step 8
Restart in normal mode and scan your computer with your Trend Micro product for files detected as RANSOM_CRYPTESLA.YYSIZ. 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.
Did this description help? Tell us how we did.