Analysis by: Erika Bianca Mendoza
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This backdoor checks the default browser by querying a certain registry. It then creates a hidden instance of the default browser and injects code into it.

The hidden browser process attempts to connect to a C&C server using port 443. Once connected, it may perform commands as instructed by the remote user.

It may then send the contents of this file to the remote server. Currently, the server is unavailable.

This backdoor may be dropped by other malware.

  TECHNICAL DETAILS

File Size: 12,288 bytes
Memory Resident: Yes
Initial Samples Received Date: 22 Aug 2011
Payload: Connects to URLs/IPs, Compromises system security, Logs keystrokes

Arrival Details

This backdoor may be dropped by the following malware:

  • TROJ_PIDIEF.ZZZ

Installation

This backdoor drops the following files:

  • %System%\dnsystem

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It drops the following copies of itself into the affected system:

  • %System%\dnsystem.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • asdfasdfa
  • asdaf3423

It injects itself into the following processes as part of its memory residency routine:

  • EXPLORER.EXE

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{07E04E55-D3D7-2575-0507-010108010706}
StubPath = "%System%\dnsystem.exe"

NOTES:

It checks the default browser by querying the registry:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
http\shell\open\command

It then creates a hidden instance of the default browser and injects code into it.

The hidden browser process attempts to connect to the following C&C server using port 443:

  • {BLOCKED}m.{BLOCKED}pgrade.info

Once connected, it may perform commands as instructed by the remote user. It logs keystrokes in the following file:

  • %System%\dnsystem

It may then send the contents of this file to the remote server. Currently, the server is unavailable.

  SOLUTION

Minimum Scan Engine: 8.900

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Remove malware files dropped/downloaded by BKDR_POISONIV.XZ

     TROJ_PIDIEF.ZZZ

Step 3

Restart in Safe Mode

[ Learn More ]

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\Active Setup\Installed Components\{07E04E55-D3D7-2575-0507-010108010706}
    • StubPath = %System%\dnsystem.exe

Step 5

Search and delete this file

[ Learn More ]
There may be some component files 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%\dnsystem

Step 6

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

Related Malware