ALIASES:

Trojan:Win32/Dynamer!ac (Microsoft); RDN/Generic Dropper!uw (McAfee); HEUR:Trojan.Win32.Generic (Kaspersky); Mal/Mdrop-BL (Sophos); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse MSIL4.ABQR (AVG)

 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:

  • 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: 223,076 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 06 Aug 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 creates the following folders:

  • %User Temp%\InstallDir

(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
winlogon = "%User Temp%\InstallDir\Server.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Skype = "%User Temp%\InstallDir\Server.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{SU7A13UE-0BU5-ME2W-G4FE-3VLD0RP0TT57}
StubPath = "%User Temp%\InstallDir\Server.exe restart"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{SU7A13UE-0BU5-ME2W-G4FE-3VLD0RP0TT57}
StubPath = "%User Temp%\InstallDir\Server.exe"

Other System Modifications

This Trojan deletes the following files:

  • %User Profile%\Windows\aTc@r.xtr

(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.)

It adds the following registry keys:

HKEY_CURRENT_USER\SOFTWARE\aTc@r

HKEY_LOCAL_MACHINE\Software\Microsoft\
Active Setup\Installed Components\{SU7A13UE-0BU5-ME2W-G4FE-3VLD0RP0TT57}

It adds the following registry entries:

HKEY_CURRENT_USER\Software\aTc@r
ServerStarted = "7/25/2014 17:46:38 PM"

HKEY_CURRENT_USER\Software\aTc@r
InstalledServer = "%User Temp%\InstallDir\Server.exe"

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\Encryptado.exe
  • %User Profile%\Windows\aTc@r.cfg
  • %User Temp%\InstallDir\Server.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.. %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.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • http://{BLOCKED}0.1:81/1234567890.functions
  • http://joaoxxk.{BLOCKED}p.org:7070/1234567890.functions

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.700

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

Restart in Safe Mode

[ Learn More ]

Step 3

Delete this registry key

[ Learn More ]

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
    • aTc@r
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Active Setup\Installed Components
    • {SU7A13UE-0BU5-ME2W-G4FE-3VLD0RP0TT57}

Step 4

Delete this registry value

[ Learn More ]

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • winlogon = "%User Temp%\InstallDir\Server.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Skype = "%User Temp%\InstallDir\Server.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{SU7A13UE-0BU5-ME2W-G4FE-3VLD0RP0TT57}
    • StubPath = "%User Temp%\InstallDir\Server.exe restart"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{SU7A13UE-0BU5-ME2W-G4FE-3VLD0RP0TT57}
    • StubPath = "%User Temp%\InstallDir\Server.exe"
  • In HKEY_CURRENT_USER\Software\aTc@r
    • ServerStarted = "7/25/2014 17:46:38 PM"
  • In HKEY_CURRENT_USER\Software\aTc@r
    • InstalledServer = "%User Temp%\InstallDir\Server.exe"

Step 5

Search and delete these components

[ Learn More ]
There may be some components that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.
  • %User Temp%\Encryptado.exe
  • %User Profile%\Windows\aTc@r.cfg
  • %User Temp%\InstallDir\Server.exe

Step 6

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %User Temp%\InstallDir

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DYNAMER.TBC. 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 this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %User Profile%\Windows\aTc@r.xtr


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