BKDR_BLADABI.KC


 ALIASES:

Backdoor:MSIL/Bladabindi (Microsoft); Trojan.Gen (Symantec); Trojan.MSIL.Zapchast.amtr (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse Generic34.COPK (AVG)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


This backdoor 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:

348,160 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

27 Mar 2015

Arrival Details

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

  • %User Profile%\Application Data\skype.exe

(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 backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
8424898cc4c927994d288319a361b825 = "%User Profile%\Application Data\skype.exe .."

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
8424898cc4c927994d288319a361b825 = "%User Profile%\Application Data\skype.exe .."

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\8424898cc4c927994d288319a361b825

It adds the following registry entries:

HKEY_CURRENT_USER\Software\8424898cc4c927994d288319a361b825
US = "!"

HKEY_CURRENT_USER\Environment
SEE_MASK_NOZONECHECKS = "1"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%User Profile%\Application Data\skype.exe = "{random characters}"

Dropping Routine

This backdoor drops the following files:

  • %System Root%\.tmp
  • %User Startup%\8424898cc4c927994d288319a361b825.exe

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %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 Details

This backdoor connects to the following possibly malicious URL:

  • {BLOCKED}6.71.116

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.750

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
    • 8424898cc4c927994d288319a361b825

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • 8424898cc4c927994d288319a361b825 = "%User Profile%\Application Data\skype.exe .."
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • 8424898cc4c927994d288319a361b825 = "%User Profile%\Application Data\skype.exe .."
  • In HKEY_CURRENT_USER\Software\8424898cc4c927994d288319a361b825
    • US = "!"
  • In HKEY_CURRENT_USER\Environment
    • SEE_MASK_NOZONECHECKS = "1"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
    • %User Profile%\Application Data\skype.exe = "{random characters}"

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.
  • %System Root%\.tmp
  • %User Startup%\8424898cc4c927994d288319a361b825.exe

Step 6

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


Did this description help? Tell us how we did.