The high pass was blocking 3-35 MHz. The other is likely a MoCA filter. If you have a MoCA network, you absolutely want that filter in place. It’s a security issue. Your entire network is accessible by anyone nearby that has a MoCA network. Every one of your devices will appear in their network as a wired device and will not require authentication. Set top boxes may have MoCA enabled - TiVO and some other DVRs use it.
You need to have a competent tech come out and take a look at your network. The fact that you have a high pass filter tells me you have something bad going on at your house that warranted dropping a high pass on your house. Of course at some point, if that’s the case, a maintenance crew will find your drop and high pass it at the tap. But with a filter that will kill your entire return path disabling your modem.
Source: corporate technical compliance for a MSO (not Comcast).
