Types of Denial of Service (DoS) Attacks
Flooding Is One of the Main Varieties of DoS Attacks
Classification of the types of DoS attacks is important because since the different types of DoS attacks employ slightly different attack mechanism, this means that the defense against them is also different. The 5 most important types of DoS attacks are described in this article.
Flood Attack
Flood attacks are the first known form of a DoS attack. The mechanism of a flood attack is simple – attackers send more traffic to a server than it can handle. If the bandwidth of the victim is good, a flood attack has a chance to succeed only if it is a DDoS.
Even if a webmaster adds more bandwidth, this still is not a sufficient protection against a flood attack. However, if the bandwidth is insufficient, even the normal volume of legitimate requests can look like a flood attack. Sometimes when a site gets traffic from popular sites, such as the front page of Digg, this could look like a DDoS attack but actually this is really legitimate traffic.
Ping of Death Attack
The Ping of Death attack is another old type of a DoS attack. Its principle is also not very sophisticated but it does manage to take advantage of a weakness in the TCP/IP protocol. A Ping of Death attack is simply sending an IP datagram, the size of which exceeds the standards.
When such a datagram is received, this crashes the receiving system. Fortunately, unless a site uses really antique equipment, Ping of Death attacks are history now because all modern equipment has defenses against such types of DoS attacks.
SYN Attack
SYN attacks also exploit a weakness in the TCP/IP protocol. When a connection is established via TCP/IP, this involves a handshaking mechanism, which consists of the exchange of SYN and ACK messages.
When a hacker floods the receiving system with SYN messages, this fills the SYN buffer. In this case the receiving party can't send an ACK messages and no TCP/IP connections with any hosts are possible.
Teardrop Attack
The Teardrop attack involves sending corrupted IP packages, the purpose of which is to confuse and potentially crash the receiving system. Similarly to the Ping of Death attack, Teardrop attacks have also become history.
Smurf Attack
The Smurf attack is one more way to paralyze a network, this time from the inside. The mechanism of a Smurf attack is more sophisticated and the critical part is to discover a broadcast server. When a hacker knows the broadcast servers in a network, he or she sends a ping request. The source IP address in this ping request is fake and it looks as if the ping comes from inside the network.
When the broadcast server receives the ping request, the ping request is sent to the entire network and all the machines in the network return a response. These responses are further redirected by the broadcast server to the target machine.
Smurf attacks are more difficult to defend against but still if a network is well planned and properly maintained, their effect shouldn't be a devastating one.
In addition to the five types of DoS attacks described here, there are some other more. Also, there are varieties of these DoS attacks but they will not be reviewed either. What's important to know is how to defend oneself against a DoS attack.
DoS Attacks Can Crash Any Server
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