BKDR_DALSK.AA
Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)
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
44,032 bytes
DLL
Yes
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
9.300
10.142.06
09 Jul 2013
10.143.00
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
Step 3
Delete this registry key
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
- IncAuthdService
- In HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services
- irpfit
- irpfit
Step 4
Delete this registry value
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"
- netsworksvc = "IncAuthdService"
Step 5
Search and delete these files
- %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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