Dynamic DNS allows a static hostname to be associated with residential or mobile computers that are assigned dynamic IP address by their ISPs.

However, this convenience comes with a potential risk to privacy in that one can easily monitor the IP address assigned to any given FQDN using basic DNS lookup tools. It is possible to track changes in the IP addresses used by a mobile user over time and, in many cases, infer the approximate geographical location of that user.

While there are legitimate uses for such monitoring, it can also represent a significant risk to the privacy of certain users. This risk is largely unrecognized by users of Dynamic DNS services.

 
The risks and benefits of Dynamic DNS monitoring are described in the following Technical Report.