This is what happen to our clent's pc when it was struck by lightning, causing her motherboard to fail completely while her network adapter got burnt. According to her she was unable to connect to the internet since the thunder storm. The LAN indicator on her modem did not light up, I reached for the adapter behind the case,  it was extremely hot that I had to power down the cpu, before taking out the adapter. Here is what I've found.

Burnt marks found on the network adapter chassis

A slightly burnt chip

Fortunately the client had an AVR unit installed in her home,  which to a certain degree prevented the blast  from reaching other components of the system such as the RAM and processor. You can assume the AVR as a second line of defense against thunderstorm.

My bet the first line of defense will be public awareness, that is not to use your pc during thunderstorms and power disturbance. Unplug the phone line from the modem and unplug the power cords going to your computer and everything that is attached to your computer (monitor, printers, etc.) when not in use. The saying goes, "what can go wrong, wil go wrongl." Play it safe and unplug your computer.