That “somone” is high likely one of the Plex AWS Servers:
When you resolve the ip 34.241.199.208, you can see that it resolves to an AWS EC2 instance.
According Full list of IPs / hostnames Plex uses for remote access? there is no official list of plex services, as instances are automaticly created/destroyed by treshhold triggers (as in usage). There is no way to fix ips for those machines. It will be any free ip from the AWS Ip range.
