Tracking pixels

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Web beacons . (English tracking bug or Web Bug , also German Web Bug , tracking pixels , IVW pixel , ivwbox , pixel tag , Pixeltag , pixel method , one-pixel image , 1 × 1 gif , Clear gif or web beacon ) are small graphics in HTML - e-mails or on websites that enable log file recording and log file analysis , which are often used for statistical evaluations for online marketing .

technology

The images, which usually only measure 1 × 1 pixel, are often transparent or created in the color of the background so that they are not visible. When a document is opened, this small image is loaded from a server on the Internet , and the download is registered there. The operator of the server can see when and how many users requested this tracking pixel or whether and when an email was opened or a website was visited.

By integrating a tracking pixel, private operators of a website can receive information about visitors without access to the server's log files. Thus on numerous websites counter ( Counter used) that are based on the same principle, but with each new visitor a new "Image" - d. H. a number increased by one - perform.

The function is usually implemented by a JavaScript call, but the term tracking pixel is still used.

example

For example the pixel-code of Piwik as a HTML - source code is installed. If Javascript is not activated in the browser used, the tracking pixel is used instead of the Javascript code in order to still register the user's access. 

<script type="text/javascript">
var pkBaseURL = (("https:" == document.location.protocol) ? "https://demo.piwik.org/" : "http://demo.piwik.org/");
 document.write(unescape("%3Cscript src='" + pkBaseURL + "piwik.js' type='text/javascript'%3E%3C/script%3E"));
</script><script type="text/javascript">
try {
   var piwikTracker = Piwik.getTracker(pkBaseURL + "piwik.php", 1);
   piwikTracker.setCookieDomain('*.piwik.org');

   if (document.domain !== 'piwik.org') {
      piwikTracker.setDocumentTitle(document.domain + "/" + document.title);
   }
   // Set the domain the visitor landed on, in the Custom Variable
   if (!piwikTracker.getCustomVariable(1)) {
      piwikTracker.setCustomVariable(1, "Domain landed", document.domain );
   }
   piwikTracker.trackPageView();
   piwikTracker.enableLinkTracking();
} catch( err ) {
}
</script>
<noscript><p><img src="http://demo.piwik.org/piwik.php?idsite=1" style="border:0" alt="" /></p></noscript>
<!-- Zusätzliches echtes Pixel für User mit deaktiviertem JavaScript -->

criticism

The tracking pixel gives the website provider access to numerous usage data and is controversial under data protection law :

  • Movement profile of the entire session ,
  • which browser and which operating system the recipient is using,
  • which IP address the recipient has; with it his internet service provider and with the help of geotargeting information about the approximate location,
  • For e-mail: whether and when the e-mail was opened.

These data can be used to improve the website. For example, it can be determined which browser versions are (still) used to a relevant extent in order to find the best time to remove "legacy". Ergonomic considerations are also possible: Frequently used links could be made more accessible and newsletters that remain unread could be reconsidered. It may also serve the user to obtain localized information.

Last but not least, with advertising-financed offers it can be helpful for the operator to document the reach of the site to the advertiser.

For the user, however, it remains unclear what happens to the information collected beyond statistical purposes. The concern here is that the information about one's own IP address, which is initially collected anonymously, combined with information from numerous other websites, results in a comprehensive interest profile. This could ultimately also be linked to a name, an e-mail address , photos, a profile in a social network, etc., so that personal rights can be violated.

Senders of spam can (if the recipient's e-mail program has a corresponding security vulnerability) by installing a tracking pixel in the e-mail, it can determine whether e-mail to a specific e-mail address is being read and whether the address is therefore valid is and is actively used.

When exploiting cross-site scripting vulnerabilities, a similar procedure is often used to transfer the victim's session identifier (session ID) to the attacker's server.

Antidote

  • If an e-mail is opened offline , the graphic of the tracking pixel cannot be loaded from the server and therefore cannot be registered there.
  • You can also use an e-mail program that does not support HTML e-mails or that can prevent the display of HTML code.
  • You can block external graphics completely in most e-mail programs and then only allow them optionally.
  • You can only grant restrictive access rights to the Internet to the mail program via the firewall .
  • Suitable browser extensions such as uBlock Origin recognize tracking pixels and can also block further tracking attempts.
  • In HTTP -Transport locally intermediary proxies such as Privoxy , Proxomitron or Webwasher Web beacons can detect under certain circumstances and stopped the call.

See also

Web links