check.labs.greynoise[.]io/
It can be hard to determine if any of your devices or your router have been compromised, but this quick test checks if your IP address has been recorded as part of a botnet's activity. A negative result doesn't guarantee that none of your devices aren't infected, or that they aren't part of a botnet, but a positive result Does mean you've got problems.
A botnet [ paloaltonetworks[.]com/cyberpedia/what-is-botnet ] is basically a collection of compromised devices that can be made to do stuff like engage in a denial of service attack at their master's request. Your IP address is basically your router's unique ID -- it's the address that a web server sends all the data to when you visit a web site. If there was no IP address, when you entered a URL in the browser nothing would happen.
Background...
The IP address points to your router, so if you got a positive test result it could be because of any one of the devices using that router, including anyone that hacked into your network. Every device connected to your router has it's own unique IP address that's normally invisible from the internet. You can disguise your IP address by going through one or more proxy servers -- a server that acts as a relay, sending your requests to whatever web site, and sending you the response it receives. VPNs use proxy severs, but encrypt the data stream between your device & that server. When you use the TOR browser it uses a string of non-logging proxy servers to better hide your identity.