Denial of Service Attacks Explained

DOS attacks (denial of service) are type of attack on a server to prevent users from consuming a particular service, usually this is an HTTP web server. This could happen by either saturating the bandwidth of the pipe going to the server or by bringing the server down to its knees so it stops taking requests all together. In this video we will learn about 3 different types of DOS attacks and explain each one by example. 0:00 Intro 2:15 Bandwidth based DOS 10:13 Max connections based DOS 16:30 Vulnerability based DOS 19:30 Summary Bandwidth based DOS - Dos Sending Huge amount of data to a server with lower bandwidth from a client with higher bandwidth which ends up saturating the server pipe and queue up future requests, new requests will have to wait or perhaps denied service. Example, the attacker have 100mb/s bandwidth (upload) the server has 10Mb/s download. If the attacker starts sending 100 mb worth of data to the server, it will take it 1 second to leave the pipe. However, The server can only download 10 mb each second for processing because thats its bandwidth, so it needs 10 seconds to completely download that 100mb and process. In this 10 seconds the server is fully busy serving just 1 client. Other requests will not be able to even reach the server, they might get queued and they may never be executed. Thus denied service. It is important to know that the server must have an end point that actually accept such large data. Like upload file with no limit. Another example, is UDP where there is no connection. - Ddos this previous scenario is less likely since servers usually has much more bandwidth than a single computer. A common attack is to do a DOS in distributed manner. Assume a server with 1 Gb and client with 10 mb/s no matter how much data the client can send it can only send 10mb per second, and the server can go through them real quick. Example, the client sends 1GB, it will leave the client’s pipe into 100 (10mb) means the client will take