DoS is an acronym for a Denial of Service (Dos) attack. The term describes any attack that denies service to users. The attack may try to overload a network or overload the ability of a computer system to respond. The attack may try to get a computer system to crash.
There are many types of denial of service attacks including:
- SYN attack - Forces the target computer to allocate so much memory for TCP connections so that it runs out of memory.
- Teardrop.c attack - Uses IP to create packet reassembly problems so the target computer crashes. Uses overlapping fragments of packets
- Ping of death - Uses IP to cause large packets to be reassembled in order to make the target computer crash.
- Land.c attack - Sends a TCP SYN packet using the target's IP address as the sender and receiver causing some systems to crash.
- Smurf attack - Floods networks with broadcasted ICMP echo request traffic to cause a network to be congested. It sends the ping as a broadcast with a spoofed sender address.
- Fraggle attack - Floods networks with broadcasted UDP echo request traffic to cause a network to be congested.
- DDOS attack - The distributed denial of service attack uses many machines to attack one system or network. One method to do this was to do a broadcast ping to an entire subnet and fake the sender of the ping making it look like the sender was the intended target (smurf attack). This would cause a flood of ping replies to the target. Attackers may also use many compromised hosts.