Ransom_CRYPTESLA.YUYAJI
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.
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:
- %Windows%\{random filename}.exe (with Administrator Privileges)
- %My Documents%\{random filename}.exe (with non-Administrator Privileges)
(Note: %My Documents% is usually C:\Documents and Settings\{user name}\My Documents on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\Documents on Windows Vista and 7.)
(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)
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 characters}-{random characters} = "%Windows%\{random filename}.exe" (with Administrator Privileges)
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{random characters}-{random characters} = "%My Documents%\{random filename}.exe" (with non-Administrator Privileges)
Other System Modifications
This Trojan modifies the following file(s):
- It encrypts files in all fixed, removable, and network drives and shares.
- It adds the extension .mp3 to the encrypted files
It adds the following registry keys:
HKEY_CURRENT_USER\Software\zzzsys
HKEY_CURRENT_USER\Software\{ID}
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
system
EnableLinkedConnections = "1"
HKEY_CURRENT_USER\Software\zzzsys
ID = "{random values}"
HKEY_CURRENT_USER\Software\{ID}
data = "{random values}"
Dropping Routine
This Trojan drops the following files:
- %User Profile%\My Documents\recover_file_{random}.txt
- %Desktop%\_ReCoVeRy_+{random}.TXT
- %Desktop%\_ReCoVeRy_+{random}.html
- %Desktop%\_ReCoVeRy_+{random}.png
- {folders containing encrypted files}\_ReCoVeRy_+{random}.html
- {folders containing encrypted files}\_ReCoVeRy_+{random}.png
- {folders containing encrypted files}\_ReCoVeRy_+{random}.txt
(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 possibly malicious URL:
- http://{BLOCKED}annel.com/wp-admin/maint/wcspng.php
- http://{BLOCKED}andphone.com/wp-content/themes/storefront/wcspng.php
- http://{BLOCKED}op.net/wcspng.php
- http://{BLOCKED}aining.com/wp-includes/theme-compat/wcspng.php
- http://{BLOCKED}feng.cn/images/lurd/wcspng.php
- http://{BLOCKED}freaknetworks.com/dev/wp-content/uploads/2015/07/wcspng.php
It deletes the initially executed copy of itself
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.YUYAJI
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 characters}-{random characters} = "%Windows%\{random filename}.exe"
- {random characters}-{random characters} = "%Windows%\{random filename}.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- {random characters}-{random characters} = "%My Documents%\{random filename}.exe"
- {random characters}-{random characters} = "%My Documents%\{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
- zzzsys
- zzzsys
- In HKEY_CURRENT_USER\Software
- {ID}
- {ID}
Step 6
Search and delete these components
- _ReCoVeRy_+{random}.html
- _ReCoVeRy_+{random}.txt
- _ReCoVeRy_+{random}.png
- %User Profile%\My Documents\recover_file_{random}.txt
Step 7
Restart in normal mode and scan your computer with your Trend Micro product for files detected as Ransom_CRYPTESLA.YUYAJI. 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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