Denial of Service (DoS) attacks

DDoS Attack diagram

A DoS attack is an attempt to make a system or server unavailable for legitimate users and, finally, to take the service down.

Though DoS attacks do not typically result in the theft or loss of significant information or other assets, they can cost the victim a great deal of time and money to handle.

How it works ?

This is achieved by flooding the server’s request queue with fake requests. After this, server will not be able to handle the requests of legitimate users.

Types of DoS attacks

In general, there are two forms of the DoS attack. The first form is on that can crash a server. The second form of DoS attack only floods a service.

flooding services

  • Buffer overflow attacks
  • ICMP flood (smurf attack or ping of death)
  • SYN flood

Crashing services

  • Teardrop attacks or IP fragmentation attacks

Distributed Denail of Service (DDoS)

DoS and DDoS

If incoming trafic orginates from diffrent machines then it is called DDos(Distributed Denial of service). Botnets (large network of compromised systems) are used for DDoS.

Reflective DDoS attacks and amplification attacks

In this kind of attack, the attacker uses a legitimate computer called reflectors to launch an attack against the victim by hiding its own IP address. The usual way is the attacker sends a small packet to a legitimate machine after forging the sender of the packet to look as if it has been sent from the victim. The legitimate machine will, in turn, send the response to the victim.

reflective DDoS

DNS amplification attacks, WordPress pingback attacks, and NTP attacks are amplification attacks. In a DNS amplification attack, the attacker sends a forged packet to the DNS server containing the IP address of the victim. The DNS server replies back to the victim instead with larger data. Other kinds of amplification attack include SMTP, SSDP, and so on.

Read more on wikipedia

wrapping up

DoS results server unavailable for legitimate users. There are flooding and crashing types of DoS attacks. Distributed DoS is more dangerous.

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