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ADW_WEBPREFIX

November 11, 2013
 ALIASES:

Trojan:Win32/Dynamer!dtc (Microsoft); [4.nsis]:Generic.dx!bcs4, [5.nsis]:Generic.dx!bcs4, [8.nsis]:Generic.dx!barw, [9.nsis]:Generic.dx!bc (McAfee); Trojan.ADH.2 (Symantec); ARC:NSIS, ARC:[nds.exe]:NSIS, ARC:[gcs.exe]:NSIS (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Dropped:Generic.Malware.Yd.99599D56 (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 OVERALL RISK RATING:
 REPORTED INFECTION:
 SYSTEM IMPACT RATING:
 INFORMATION EXPOSURE:

  • Threat Type: Adware

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This adware 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:

640,686 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

03 Oct 2012

Arrival Details

This adware 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 adware creates the following folders:

  • %System Root%\DOCUME~1
  • %System Root%\DOCUME~1\Wilbert
  • %User Profile%\LOCALS~1
  • %User Temp%\nsb2.tmp
  • %User Profile%\LOCALS~1\TempNd

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %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.. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
nds = "%User Profile%\TempNd\nds.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
gcs = "%User Profile%\TempNd\gcs.exe"

Other System Modifications

This adware deletes the following files:

  • %User Temp%\nsl1.tmp
  • %User Temp%\nsb2.tmp

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
Zones\3
1001 = "0"

(Note: The default value data of the said registry entry is 1.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
Zones\3
1004 = "0"

(Note: The default value data of the said registry entry is 3.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Internet Settings\
Zones\3
1201 = "0"

(Note: The default value data of the said registry entry is 3.)

Dropping Routine

This adware drops the following files:

  • %User Temp%\nsb2.tmp\System.dll
  • %User Profile%\TempNd\ndc.exe
  • %User Profile%\TempNd\ndck.exe
  • %User Profile%\TempNd\sites.txt
  • %User Profile%\TempNd\sites2.txt
  • %User Profile%\TempNd\nds.exe
  • %User Profile%\TempNd\gcs.exe
  • %User Temp%\nsb2.tmp\Processes.dll

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.. %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.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

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 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
    • nds = "%User Profile%\TempNd\nds.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • gcs = "%User Profile%\TempNd\gcs.exe"

Step 4

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3
    • From: 1001 = "0"
      To: 1001 = ""1""
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3
    • From: 1004 = "0"
      To: 1004 = ""3""
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3
    • From: 1201 = "0"
      To: 1201 = ""3""

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.
  • %User Temp%\nsb2.tmp\System.dll
  • %User Profile%\TempNd\ndc.exe
  • %User Profile%\TempNd\ndck.exe
  • %User Profile%\TempNd\sites.txt
  • %User Profile%\TempNd\sites2.txt
  • %User Profile%\TempNd\nds.exe
  • %User Profile%\TempNd\gcs.exe
  • %User Temp%\nsb2.tmp\Processes.dll

Step 6

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %System Root%\DOCUME~1
  • %System Root%\DOCUME~1\Wilbert
  • %User Profile%\LOCALS~1
  • %User Temp%\nsb2.tmp
  • %User Profile%\LOCALS~1\TempNd

Step 7

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

Step 8

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %User Temp%\nsl1.tmp
  • %User Temp%\nsb2.tmp


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