Analysis by: Adrian Cofreros
ALIASES:

VBS/Kryptik.X trojan(NOD32)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This worm arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

  TECHNICAL DETAILS

File Size: 303,281 bytes
Memory Resident: Yes
Initial Samples Received Date: 15 Dec 2013

Arrival Details

This worm 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 worm drops the following copies of itself into the affected system:

  • %User Profile%\{malware file name}.vbs

(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.)

Autostart Technique

This worm adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{malware file name} = "wscript.exe //B "%User Profile%\{malware file name}.vbs""

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{malware file name} = "wscript.exe //B "%User Profile%\{malware file name}.vbs""

It drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\{malware file name}.vbs

(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 worm adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\{malware file name}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\{malware file name}
(Default) = "{true/false} - {date executed}"

Propagation

This worm drops the following copy(ies) of itself in all removable drives:

  • {removable drive letter}:\{malware file name}.vbs

Other Details

This worm connects to the following possibly malicious URL:

  • http://{BLOCKED}r.no-ip.biz:88/is-ready

NOTES:

This worm drops shortcut files pointing to the copy of itself in removable drives. These dropped .LNK files use the names of the folders and files located on the said drives for their file names. It then sets the attributes of the original folders to System and Hidden to trick the user into clicking the .LNK files.