MoCa Help request

Hi. Hoping to get help with setting up MoCA.

I have an Xfinity XB8 Gateway and a Gigabyte plan. It is on the second floor. I get very good coverage throughout the house, even in the basement two floors below. Comcast wired the house when we moved in 30 years ago for televisions. We have since redone the basement and I really don't know where coaxial splitters are behind walls.

I have a coaxial outlet not in use in the basement next to a Mac mini which I use primarily as a media server. Although it's working fine and I get download speeds about 400 Mbps on it wirelessly, I was looking in to MoCa. I read a bit beforehand and didn't think it would work for me because of all the warnings I read about having the appropriate splitters, etc. I was curious to try and picked up an inexpensive MoCa box, plugged it into the coax outlet and then connected the Mac mini to it via ethernet cable. I was amazed that I even had an internet connection, let alone speeds over 900 Mbps.

My question is about security and whether I am really going to interfere with neighbors' signal. My immediate neighbors use fiberoptic. I have read warnings to use a PoE filter. Since I don't have access to the splitters, I don't know where to put it. I live in a very residential neighborhood of single family homes and am wondering if my home network is at a real risk. 

Thanks very much for any guidance.