DOS attacks,DDOS and REFLECTIVE DDOS attack

DOS: Denial of service.
A type of attack, in which the attacker uses total bandwidth of the target website, and crashes it.As there are legitimate users who already are using the bandwidth, the job of attacker becomes pretty much easy.
In this attack, the total bandwidth is used, therefore legitimate users are also not allowed to access it.
In DOS attacks there is only one attacker who tries to crash the target system using his ‘single’ system.



 DDOS (Distributed DOS) attack
In this attack the attacker uses his system to break into a smaller less secure network, and gets control on the entire network.This gives the attacker the power to use all the computers in that network. Attacker then uses that entire computer network to attack the target system. As many computersare attacking the target system at the same point of time, this attack is called Distributed DOS attack i.e. DDOS attack.In DOS attack, as only a single attacker is attacking the target system, this attack is not too dangerous and can be easily countered. But in DDOS attacks, multi-leveled attackers are involved, so it makes this kind of attacks more dangerous and definitely very hard to counter.

 Reflective DDOS attacks
The attacker uses the spoofed IP address of the target system to send infinite no. of SYN packets to a large popular website on the internet, making sure that the website will reply to all the SYN packets.What happens in this is when the website sends replies to all the SYN packets they arereceived by the target system, and due to large number of replies the target systembandwidth gets flooded, and hence crashes.

NOTE: Reflective DDOS attacks are more dangerous as compared to DOS and DDOS attack.