Analysis by: Christopher Daniel So
ALIASES:

Backdoor:Win32/Daserf.A (Microsoft); Mal/Emogen-Y (Sophos)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

This backdoor may be dropped by other malware.

  TECHNICAL DETAILS

File Size: 33,004 bytes
File Type: PE
Memory Resident: Yes
Initial Samples Received Date: 13 Jan 2011

Arrival Details

This backdoor may be dropped by other malware.

Installation

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

  • %System%\msnws.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 drops the following files:

  • %System%\usid.dat

(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.)

Autostart Technique

This backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\msblues
DisplayName = "Microsoft Devices Mapping Service"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\msblues
ErrorControl = 1

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\msblues
ImagePath = "%System%\msnws.exe"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\msblues
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\msblues
Start = 2

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\msblues
Type = 16

  SOLUTION

Minimum Scan Engine: 8.900
VSAPI PATTERN File: 7.768.16
VSAPI PATTERN Date: 14 Jan 2011
VSAPI PATTERN Date: 1/14/2011 12:00:00 AM

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

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
    • msblues

Step 4

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%\usid.dat

Step 5

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