TROJ_DROPPER.KAA

July 27, 2013
 ALIASES:

VirTool:Win32/Vtub.GA (Microsoft); [00007005.EXE]:BackDoor-CEP.gen (McAfee); Backdoor.Prorat (Symantec); Trojan-Dropper.Win32.VB.gvl, Trojan-Dropper.Win32.VB.bsi (Kaspersky); Trojan.Win32.Generic!SB.0 (Sunbelt); Trojan.Generic.531567 (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 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.

It disables Task Manager, Registry Editor, and Folder Options.

  TECHNICAL DETAILS

File Size:

138,054 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

07 May 2012

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.

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{9D71D88C-C598-4935-C5D1-43AA4DB90836}
stubpath = "%Program Files%\msn\msn.exe s"

Other System Modifications

This Trojan deletes the following files:

  • %Program Files%\msn\msn.exe

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

It adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{9D71D88C-C598-4935-C5D1-43AA4DB90836}

HKEY_LOCAL_MACHINE\SOFTWARE\Bifrost

HKEY_CURRENT_USER\SOFTWARE\Bifrost

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Bifrost
nck = "{random values}"

HKEY_CURRENT_USER\Software\Bifrost
klg = "{random values}"

HKEY_CURRENT_USER\Software\Bifrost
plg1 = "{random values}"

It creates the following registry entry(ies) to disable Task Manager, Registry Tools and Folder Options:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableRegistryTools = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = "1"

Dropping Routine

This Trojan drops the following files:

  • %Windows%\battemp.bat
  • %User Profile%\Application Data\addons.dat
  • %Program Files%\msn\msn.exe

(Note: %Windows% is the Windows folder, which is usually C:\Windows.. %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.. %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

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

Enable Registry Editor, Task Manager, and Folder options

[ Learn More ]
By doing this step, you also enable other applications/programs disabled by this malware/grayware/spyware.

Step 4

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\Microsoft\Windows\CurrentVersion\Policies
    • System
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components
    • {9D71D88C-C598-4935-C5D1-43AA4DB90836}
  • In HKEY_LOCAL_MACHINE\SOFTWARE
    • Bifrost
  • In HKEY_CURRENT_USER\SOFTWARE
    • Bifrost

Step 5

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\Active Setup\Installed Components\{9D71D88C-C598-4935-C5D1-43AA4DB90836}
    • stubpath = "%Program Files%\msn\msn.exe s"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Bifrost
    • nck = "{random values}"
  • In HKEY_CURRENT_USER\Software\Bifrost
    • klg = "{random values}"
  • In HKEY_CURRENT_USER\Software\Bifrost
    • plg1 = "{random values}"

Step 6

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.
  • %Windows%\battemp.bat
  • %User Profile%\Application Data\addons.dat
  • %Program Files%\msn\msn.exe

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DROPPER.KAA. 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.

  • %Program Files%\msn\msn.exe


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