You live in an are that is susceptible to lightning (most of the world). You use a power strip or UPS with surge protection. Surge protection is made possible via a MOSFET (metal-oxide semi-conductor field effect transistor) that is destroyed when the power surges to potentially destructive levels. You do not have surge protection on the coaxial cable to the coaxial modem. You are concerned that if lightning were to strike, the surge could run through the coaxial cable and into the cable modem thus destroying the cable modem itself and the device(s) that is (are) connected to it via an ethernet patch cable. Should you be concerned that the spike in current could hurt your laptop from the cable modem over the network cable?
Yes. You should be concerned. Many UPSes have coaxial input and output jacks to protect against these surges. Luckily in our experience, the speed degradation is negligible. Your internet performance should not be significantly affected.