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BKDR_DALSK.AA

July 09, 2013
 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: 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.

It is a component of other malware.

It requires its main component to successfully perform its intended routine.

  TECHNICAL DETAILS

File Size:

44,032 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

03 Jul 2013

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 is a component of other malware.

Other System Modifications

This backdoor adds the following registry keys:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\IncAuthdService

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\irpfit

It adds the following registry entries:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows NT\CurrentVersion\Svchost
netsworksvc = "IncAuthdService"

Dropping Routine

This backdoor drops the following files:

  • %System%\drivers\irpfit.sys

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

Other Details

This backdoor requires its main component to successfully perform its intended routine.

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

10.142.06

FIRST VSAPI PATTERN DATE:

09 Jul 2013

VSAPI OPR PATTERN File:

10.143.00

VSAPI OPR PATTERN Date:

09 Jul 2013

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_LOCAL_MACHINE\System\CurrentControlSet\Services
    • IncAuthdService
  • In HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services
    • irpfit

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 NT\CurrentVersion\Svchost
    • netsworksvc = "IncAuthdService"

Step 5

Search and delete these files

[ Learn More ]
There may be some 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%\drivers\irpfit.sys

Step 6

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


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