Published June 18, 2018

What is a User Agent?

A user agent is software that performs actions for the user of a computer. The most common type of user agent is a web browser (like Internet Explorer, Chrome, Firefox, and Safari), which collects and shares data on behalf of the person using the service.

While user agents themselves are fairly simple to understand, what data they collect (as well as how they share it) can get more complicated. For instance, most browsers will openly share the type of browser, browser version, operating system, and language to the websites that the user is browsing. Essentially, the “user-agent string” containing this information is sent to a website to help it determine what to display.

What is User Agent Spoofing?

When sending out a user-agent string, a user’s browser sometimes identifies as another browser to “spoof” a website. Spoofing came about because some websites were only displayed on particular web browsers. This led companies to find work-arounds, so they would pretend to be other browsers to avoid being blocked from accessing a website.

For example, a site that would only display in a Netscape browser might be sent a user-agent string from Internet Explorer that appeared to be from Netscape. The site would then display as normal.

While most websites will display on any web browser today, spoofing is still frequently seen during fraudulent activity. Malicious bots use this technique to not only mask the fact that they are a bot, but also make it so that they appear to be using a known web browser (when in reality, they aren’t viewing a browser at all).

In fact, bots can create multiple user-agent strings with various combinations of browsers, versions, and operating systems to make them appear like multiple people. When the website returns the content to display to these requests, the bots can carry out impression and click fraud on the advertisements that are shown.

Despite bots being able to employ these kinds of techniques, there are ways to identify unseen browsers and simultaneous user-agent requests. From looking for outdated browser versions to finding multiple browser requests from the same IP address, NS8 Protect and NS8 TrueStats recognize false user strings and unseen browsers. This allows them to tag suspicious traffic, helping you prevent user-agent spoofing and other fraud attacks on your digital advertising.

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