Detecting and tracking unique devices is an important part of click fraud detection and protection, making it possible to record and use highly actionable data for every interaction with your website after an ad click.

Device tracking is done with the website tracking code that needs to be installed in order for tracking to work.

Why auto-block IP when device is unknown?

There are many reasons why ClickGUARD could be unable to detect the unique device after a paid click, including:

Visitor is blocking JavaScript (who does this in 2018?), meaning it's very likely it is a bot
Visitor leaves the landing page immediately upon getting there (bounces) - likely a malicious or invalid click, also very likely came from a bot
Visitor is using a kind of a script or browser plug-in that is blocking standard tracking used in advertising, which is suspicious

How to turn on auto-blocking for unknown devices

This is considered to be an aggressive blocking option, but an option that could save a significant portion of your advertising budget. You can enable it in Settings -> Auto-Blocking: