If you haven’t heard about it by now, there is a recent exploit that allows a maliciously designed website to trigger a reset of certain ARRIS (formerly Motorola) Cable Modems.
This doesn’t affect all of them, but only a certain model. However, if you’re paranoid at all, there is no harm in blocking access to the cable modem.
There are two ways to do this: drop all traffic to the cable modem (which doesn’t affect internet traffic), or to filter out the specific URL used to do this.
And we cover both methods