1) If your internet is working for some applications and not others (i.e. skype works but WoW is lagging out) then you are NOT being DDoS'd. In most cases it means the DNS server you use is not working properly (comcast DNS servers are shit). If you have not set a DNS server then you are probably using your Internet Service Providers IP. I recommend switching to Google's or OpenDNS's server. Here's how:
http://i.imgur.com/I2VGU.png > right click your current connection and go to properties > press Internet Protocol Version 4 > properties > http://i.imgur.com/edr62.png
Mine is set to google's DNS servers, you can use whichever you want.
2) DDoS. You know you're being DDoSd if you gradually begin to lag on all programs using the internet and then disconnect from them. Sudden disconnects usually do not involve DDoS. People that DDoS you usually obtain your IP through skype or twitch tv and the amount of people that can DDoS you on the spot is surprisingly low **Do not go to DDoS as the first thing you blame when you disconnect from WoW**
But here is how to stop DDoS if you know you're being DDoSd:
Log into your router > find your mac address (should look like this http://i.imgur.com/6X5oc.png)> change one of the numbers to another number > save your settings and restart your modem
Don't change your mac address too many times per day as it might cause some problems with your ISP but this should change your IP making it impossible for the DDoSer to target you unless he/she gets your new IP (through skype/twitch/etc). Note: Doing ipconfig/release or restarting your modem/router alone will not stop DDoS.
Further Protection: If your attacker keeps finding your IP after changing your mac address try getting a VPN program like HotSpot Shield to "spoof" your IP after you have changed it.
Edit: More stuff to spoof your IP (use whichever lags you the least)
Edited by aquatics, 28 February 2012 - 05:57 AM.