TROJ_CRYPTOWALL.J
Ransom:Win32/Crowti.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 deletes the initially executed copy of itself.
TECHNICAL DETAILS
245,760 bytes
Yes
20 Feb 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:
- %System Root%\{Random 8 Characters}\{Random 8 Characters}.exe
- %Application Data%\{Random 8 Characters}.exe
(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %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.)
It creates the following folders:
- %System Root%\{Random 8 Characters}
(Note: %System Root% is the Windows root folder, where it usually is C:\ 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 8 Characters} = "%Application Data%\{Random 8 Characters}.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{First 7 Characters of {Random 8 Characters}} = "%System Root%\{Random 8 Characters}\{Random 8 Characters}.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
*{Second to the Sixth Characters {Random 8 Characters}} = "%System Root%\{Random 8 Characters}\{Random 8 Characters}.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
*{Last Seven Characters of {Random 8 Characters}} = "%Application Data%\{Random 8 Characters}.exe"
It drops the following file(s) in the Windows Startup folder to enable its automatic execution at every system startup:
- %User Startup%\{Random 8 Characters}.exe
(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)
Other System Modifications
This Trojan adds the following registry keys:
HKEY_CURRENT_USER\Software
Local AppWizard-Generated Applications =
HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications
WebBrowse =
HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications\
WebBrowse
Recent File List =
HKEY_CURRENT_USER\Software\Local AppWizard-Generated Applications\
WebBrowse
Settings =
Other Details
This Trojan connects to the following possibly malicious URL:
- http://{BLOCKED}a87.com/img2.php?{Random Letter}={Random Value}
- http://{BLOCKED}r.com/img4.php?{Random Letter}={Random Value}
- http://{BLOCKED}s.org/img4.php?{Random Letter}={Random Value}
It deletes the initially executed copy of itself
NOTES:
This Trojan encrypts files with certain extensions in the affected system hard drive. It drops the files HELP_DECRYPT.HTML, HELP_DECRYPT.PNG, HELP_DECRYPT.TXT, and HELP_DECRYPT.URL to all folders where files are encrypted.