Usually a good way to see if this is foul play and not your ISP is to open up a browser while the dc or ping spike is happening in game and open up any webpage to see how fast (or slow) it loads. DDos attempts **usually ** focus just on your client's communication with the server at any point, and not on any other aspect on your internet.
P.S. I put "usually" in bold for the sake of the off chance I'm wrong about some details. I'm merely speaking from personal experience of such events and haven't noticed and/or experienced a full on internet shutdown.