1. Symantec/
  2. Security Response/
  3. Trojan.StartPage


Risk Level 1: Very Low

January 15, 2002
April 29, 2010 3:15:01 PM
Systems Affected:
Trojan.StartPage is a detection for Trojan horse threats that change a browser’s home page. The reasons for changing the home page vary, though it is commonly done to display advertising to the user, exploit the browser to run other threats, or to promote misleading applications.

Background information
Trojan.StartPage threats are one of the simpler Trojans in the threat landscape. In most cases their sole purpose is the change the home page of a browser on the compromised computer. The home page is the predetermined website that a browser opens when it starts. It can be customized to point to a local .html file or a URL on the Internet.

Simple, but effective, these Trojans are often used as a means to an end, where the attacker can put whatever he or she likes in the .html file or on the domain that the browser now opens to. When the browser is started, the page is loaded, performing whatever function the attacker had in mind.

Which browsers are susceptible to these threats?
Pretty much any browser can fall prey to these sorts of threats. However, the Trojans in today’s threat landscape tend to target Internet Explorer almost exclusively. This browser’s popularity is likely what makes it such a target, but that is not to say a user shouldn’t be careful when using other browsers as well.

How do these threats work?
These Trojans arrive on a computer in much the same way as other Trojan horses. When the Trojan is executed it may not appear to do anything. However, it usually silently runs code that changes the home page in the browser, which will be apparent the next time the browser is opened.

Most browsers contain a setting within their user options to customize the home page to point to any website they wish. This change can also be scripted, where the Trojans can run a few lines of code to silently change this setting.

What are the risks of these threats?
Many of these Trojans result in basic annoyance, where the user is served up advertisements or unwanted promotional material every time they open their browser. However, an attacker, once they’ve redirected the home page to an arbitrary URL, can serve up whatever sort of content they wish.

For example, an attacker could theoretically set up an exploit for a browser vulnerability on the Web page used as the home page. When a user starts their browser, the exploit is run and their computer is compromised. If the browser vulnerability is severe enough, the attacker could take complete control of the computer.

What is the purpose of these threats?
In the case of advertising, many affiliates are paid based on the amount of traffic they bring to a chosen website. Unscrupulous affiliates sometimes generate this type of Trojan as a quick way to increase their affiliate hits on a given website, thus increasing the amount of revenue they can generate through a particular website’s affiliate program.

Are there any tell-tale signs?
If you find the home page on your browser has inexplicably changed to an unfamiliar or unwanted Web page, a Trojan of this type may be responsible. However, some non-malicious programs change the home page during their installation routines as well. While a change to your home page may be annoying, it is not always indicative of a Trojan.StartPage infection.

What can I do to minimize the risks?
As a general rule, users should always run up-to-date antivirus software with real-time protection such as Norton Antivirus, Norton Internet Security, Norton 360 or Symantec Endpoint Protection. In addition, a firewall -- or better still, an Intrusion Prevention System (IPS) -- will help to block download activities initiated by these types of malicious programs. Program controls such as those found in Symantec Endpoint Protection can also help to prevent programs such as these from executing in the first place.

How can I find out more?
Advanced users can submit a sample to Threat Expert to obtain a detailed report of the system and file system changes caused by a threat.


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.
Writeup By: Ben Nahorney
Summary| Technical Details| Removal

Search Threats

Search by name
Example: W32.Beagle.AG@mm
STAR Antimalware Protection Technologies
2016 Internet Security Threat Report, Volume 21
  • Twitter
  • Facebook
  • LinkedIn
  • Google+
  • YouTube