Denial of Service attacks

The two most devastating variations of Denial of Service attacks are the distributed denial of service (DDoS) and the distributed deflection denial of service (DrDoS). Both types enlist the assistance of others, voluntary or not, to assist in the attack. This significantly increases the size of the attack, shields the source, and makes defending from it harder.


1 Physical destruction of router (OR)

2 Link layer attacks (OR)

2.1 Protocol attack using link layer protocol (OR)
2.2 Physical link attack

3 ARP attacks (OR)

4 IP attacks (OR)

4.1 ICMP Message (OR)
4.1.1 Ping O' Death: Send one or more oversized ping packets (larger than 65,536 bytes) (OR)
4.1.2 Malformed
4.2 IP Fragmentation Attack

5 UDP attacks (OR)

6 TCP attacks (OR)

6.1 TCP SYN Flood: Trick target into thinking a session is being established by creating half-open connections (OR)
6.2 Connect() (OR)
6.4 New/undiscovered DoS against TCP

7 Application-Layer DoS (OR)

7.1 Telnet (OR)
7.2 SSH (OR)
7.3 SNMP (OR)
7.4 HTTP (OR)
7.4.1 HTTP Flood (OR)
7.4.2 Long form field submission through POST method (OR)
7.4.3 Partial requests (OR)
7.4.4 Junk HTTP GET and POST requests
7.5 Other application layer protocol

A DoS is distributed from only one starting point, whereas a DDoS implies several computers or servers. Amplification is dependent on the amount of zombies in the botnet used. In UDP spoofing the IP address of the packet (where it comes from) is replaced by the IP address of the target. The answers to the sent packets will thus come back to the target, and not to the attacker. Amplification is dependent on the number of zombies in the botnet and the used protocol (attack vector). Everything that works on UDP presents a good amplification factor and allows spoofing are prime candidates, such as game servers, time servers (NTP) or Domain Name Servers.


1. UDP (User Datagram Protocol) spoofing

2 Create zombies

2.1 Voluntary “botnet”

3 Launch DoS vector

3.1 UDP Flood (OR)
3.2 TCP SYN Flood (OR)
3.3 ICMP echo request Flood (OR)
3.4 ICMP directed broadcast (like smurf)
3.5 NTP Flood
3.6 Another UDP based protocol whose answers are longer than the questions


1 IP spoofing

1.1 Call a large number of servers (DNS, NTP, Game servers) using a legitimate UDP request (amplification coefficient of between 20 and 50)
1.2 Call a large number of servers using a TCP SYN request (amplification coefficient of 10)