Doesn't need to take control of multiple devices. Can even be a syndicate of many computer users 'attacking' the server at the same time.How to really trace out? Isnt ddos is by a hacker controlling multiple device to keep connecting to server?
DDoS is simply flooding the server with many user requests to the point that the server cannot service the incoming requests fast enough. All resources are used up, and the server either slows down due to hardware limitations or crashes pre-maturely to protect data integrity. Main aim of DDoS attacks is to send so many requests that the server would need to take weeks/months/years to finish serving all requests or take out the server by crashing it.
There is no way to trace the attack unless u can determine the source of attack. Even then, what can you do? The attacker will just assume another IP address and continue his intention. The current and only way out is to build a firewall that has a strong algorithm to sieve out potentially high volume traffic coming from a single or a group of sources. Requires pattern recognition, so how good a server performs depends on how secure the server provider can be.

