Analysis by: Sabrina Lei Sioting

ALIASES:

Trojan:Win32/Startpage.AR (Microsoft), Trojan.Win32.StartPage.y (Kaspersky), StartPage-Q (McAfee), Troj/StartPa-R (Sophos), TR/StartPage.at (Antivir), Trojan.Startpage.Y (Clamav), W32/StartPage.Y!tr (Fortinet), Trojan.Win32.StartPage (Ikarus), Win32/StartPage.Y3 trojan (Eset), Trojan Adware/Startpage.X (Panda),

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It modifies the affected system's HOSTS files. This prevents users from accessing certain websites.

However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size: 57,344 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 01 Sep 2012

Arrival Details

This Trojan 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 Trojan drops the following files:

  • %Windows%\default.css
  • %Windows%\Web\win.def

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

Other System Modifications

This Trojan adds the following registry entries as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer
Search = "http://{BLOCKED}nt-all.com/--/?pgdoc "

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer
SearchURL = "http://{BLOCKED}nt-all.com/--/?pgdoc "

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Default_Search_URL = "http://{BLOCKED}nt-all.com/--/?pgdoc "

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Default_Page_URL = "http://{BLOCKED}nt-all.com/-/?pgdoc "

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Use Search Assistant = "yes"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Search Bar = "http://{BLOCKED}nt-all.com/---/?pgdoc "

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer
Search = "http://{BLOCKED}nt-all.com/--/?pgdoc "

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
Use Search Assistant = "yes"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Styles
User Stylesheet = "%Windows%\default.css"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Styles
Use My Stylesheet = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Search
CustomizeSearch = "http://{BLOCKED}nt-all.com/--/?pgdoc "

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Search
SearchAssistant = "http://{BLOCKED}nt-all.com/---/?pgdoc "

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Styles
User Stylesheet = "%Windows%\Web\win.def"

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Styles
Use My Stylesheet = "1"

It modifies the following registry key(s)/entry(ies) as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Start Page = "http://{BLOCKED}nt-all.com/-/?pgdoc about:blank "

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

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main
Search Page = "http://{BLOCKED}nt-all.com/--/?pgdoc "

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
Default_Search_URL = "http://{BLOCKED}nt-all.com/--/?pgdoc "

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
Search Page = "http://{BLOCKED}nt-all.com/--/?pgdoc "

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Main
Start Page = "http://{BLOCKED}nt-all.com/-/?pgdoc about:blank "

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Search
SearchAssistant = "http://{BLOCKED}nt-all.com/---/?pgdoc "

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Internet Explorer\Search
CustomizeSearch = "http://{BLOCKED}nt-all.com/--/?pgdoc "

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

It adds the following registry keys as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Search

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Styles

HOSTS File Modification

This Trojan adds the following strings to the Windows HOSTS file:

  • {random numbers} auto.search.msn.com

Other Details

However, as of this writing, the said sites are inaccessible.

  SOLUTION

Minimum Scan Engine: 9.200

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

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer
    • Search
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer
    • Styles

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\Internet Explorer
    • Search = "http://{BLOCKED}nt-all.com/--/?pgdoc"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer
    • SearchURL = "http://{BLOCKED}nt-all.com/--/?pgdoc"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • Default_Search_URL = "http://{BLOCKED}nt-all.com/--/?pgdoc"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • Default_Page_URL = "http://{BLOCKED}nt-all.com/-/?pgdoc"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • Use Search Assistant = "yes"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • Search Bar = "http://{BLOCKED}nt-all.com/---/?pgdoc "
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer
    • Search = "http://{BLOCKED}nt-all.com/--/?pgdoc"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
    • Use Search Assistant = "yes"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Styles
    • User Stylesheet = "%Windows%\default.css"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Styles
    • Use My Stylesheet = "1"

Step 4

Restore this modified 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\Internet Explorer\Main
    • From: Start Page = "http://{BLOCKED}nt-all.com/-/?pgdoc about:blank "
      To: Start Page = {default}
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main
    • From: Search Page = "http://{BLOCKED}nt-all.com/--/?pgdoc"
      To: Search Page = {default}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
    • From: Default_Search_URL = "http://{BLOCKED}nt-all.com/--/?pgdoc"
      To: Default_Search_URL = {default}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
    • From: Search Page = "http://{BLOCKED}nt-all.com/--/?pgdoc"
      To: Search Page = {default}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main
    • From: Start Page = "http://{BLOCKED}nt-all.com/-/?pgdoc about:blank "
      To: Start Page = {default}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Search
    • From: SearchAssistant = "http://{BLOCKED}nt-all.com/---/?pgdoc"
      To: SearchAssistant = {default}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Search
    • From: CustomizeSearch = "http://{BLOCKED}nt-all.com/--/?pgdoc"
      To: CustomizeSearch = {default}

Step 5

Remove these strings added by the malware/grayware/spyware in the HOSTS file

[ Learn More ]
     {random numbers} auto.search.msn.com
"

Step 6

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.
  • %Windows%\default.css
  • %Windows%\Web\win.def

Step 7

Scan your computer with your Trend Micro product to delete files detected as TROJ_STARTPAGE.SS. 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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