Here at Vokke we use PRTG as a tool to monitor all of our infrastructure components. We needed to monitor some Sender Policy Framework (SPF) DNS records (the modern, TXT-based ones) and there wasn’t a sensor for it. So, we built one!

All the code is freely available here on Github for both x86 and x64 Windows environments.

About this sensor

This is a sensor for PRTG that allows you to monitor whether specific IP addresses pass an SPF check for a given domain according to the SPF definition in RFC4408. The IP address and domain are passed as command line arguments.

This sensor is a Node.js project bundled as a PE/exe file through Pkg. If you don’t like the idea of downloading a binary from Git, you can run the Pkg command yourself.

How to use

You can use this sensor in two ways. The first is to check whether an IP address passes the SPF conditions on the domain:

spf-checker.exe --checkType=ip --ipAddress=45.3.23.5 --domain=myDomain.com

The second is to simply ensure that a keyword is present within the SPF TXT record:

spf-checker.exe --checkType=keyword --keyword=mailgun --domain=myDomain.com

Photo by Annie Spratt on Unsplash