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TROJ_DYNAMER.LXN

February 18, 2014
 Analysis by: Mark Joseph Manahan
 ALIASES:

Troj/MSIL-KH (Sophos) ,W32/Generic!tr (Fortinet) ,Win32.SuspectCrc (Ikarus) ,Trojan:Win32/Dynamer!ac (Microsoft) ,RDN/Generic.dx!c2l (McAfee) ,a variant of Generik.DPTCMUP trojan (Eset) ,Trojan.Win32.Generic!BT (Sunbelt)

 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: 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.

  TECHNICAL DETAILS

File Size:

679,936 bytes

File Type:

EXE

Initial Samples Received Date:

06 Feb 2014

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:

  • %User Temp%\svchost.exe

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
ba4c12bee3027d94da5c81db2d196bfd = ""%User Temp%\svchost.exe" .."

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
ba4c12bee3027d94da5c81db2d196bfd = ""%User Temp%\svchost.exe" .."

It enables its automatic execution at every system startup by dropping the following copies of itself into the Windows Common Startup folder:

  • %User Startup%\ba4c12bee3027d94da5c81db2d196bfd

(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\ba4c12bee3027d94da5c81db2d196bfd

It adds the following registry entries:

HKEY_CURRENT_USER\Software\ba4c12bee3027d94da5c81db2d196bfd
US = ""

HKEY_CURRENT_USER\Environment
SEE_MASK_NOZONECHECKS = "1"

It creates the following registry entry(ies) to bypass Windows Firewall:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%User Temp%\svchost.exe = "%User Temp%\svchost.exe:*:Enabled:svchost.exe"

Other Details

This Trojan connects to the following possibly malicious URL:

  • {BLOCKED}gned.{BLOCKED}z.net