UDP Flooder DDOS ATTACK – A Concise Guide For 2021


UDP (User Datagram Protocol) is a protocol in networking which is bereft of a session and connection and operates on the IP (Internet Protocol) while transmitting datagrams that are UDP define over a network of host machines. 

  1. What is UDP Flood DDOS attack?
  2. Signs of UDP flood attack
  3. Why they are dangerous
  4. How to prevent it?

1) What is UDP Flood DDOS attack?

UDP flood is a form of attack through denial of service (DoS), where the attacker overwhelms random host ports with IP garbage UDP flooder packets using a UDP datagram. Let us understand what is UDP in networking. Since the host looks for applications associated with the datagram, it sends a “destination unreachable” ICMP packet on being unable to find any port connected to the server and thus detect such information. With a multitude of such UDP flooder packets and a number of machines sending such packets flooding the system, it becomes overburdened and unresponsive to the internet. Many such attacks also provide total anonymity by spoofing their IP address for return of the ICMP UDP flooder packets. 

2) Signs of UDP flood attack

Whenever a UDP service server receives UDP packets, it firstly ascertains if any program is running at the specific port(s). If no such UDP flooder packets are detected, it issues an ICMP packet notifying the sender that the UDP flooder packet did not reach its destination. With a volumetric increase of such packets from multiple machines causing a UDP flooder packet flood and congestion well beyond the link capacity to the internet, it causes a UDP DDoS attack (Distributed Denial of Service).

Some signs to detect a DDoS attack are 

  • Frequent internet disconnection.
  • Slow access to files, either remote/ local.
  • Website access issues.
  • Inability to access particular websites.
  • Excessive volumes of spam emails.

If two or more of these UDP flooder issues persist over the long term, one can be relatively certain of a DDoS attack.

3) Why they are dangerous

What is UDP used for? UDP is popular in VoIP and chats since it doesn’t need to be rechecked by the 3-way handshake like the TCP protocol and hence has lower overheads. The UDP networking protocol is both connectionless and session-less and can be used to send a large volume of UDP flooder traffic to any host. Exploiting the fact that no internal protection can limit the rate of UDP flood attacks, the attacks become exceptionally dangerous and can be successful with limited resources.

Some of the consequences are

  • Loss of confidential data
  • Loss of productivity
  • Reputational damage etc.

4) How to prevent it?

At the basic level, most operating systems traditionally limit the ICMP response rate to gain UDP flood protection. However, with such unselective filtering, many UDP flood attack detects solutions block legitimate packets, causing congestion and reducing the speed of the connection upstream, causing disruptions to the internet. Even the firewalls that block malicious UDP flooder packets are not over-provisioned for such volumetric modern attacks allowing the firewall to be surpassed.

But, Anycast technology which uses deep-packet UDP flooder inspection is successful in balancing the load across a network of scrubbing servers during an attack. They use proprietary scrubbing software, specially designed to rely on a combination of factors like abnormal attributes, IP reputation, suspicious behaviour etc. in the UDP packets, to process inline traffic with ‘Incapsula’ identifying and filtering out such malicious DDoS packets. Such processing has zero-delays, is performed on-edge, and ensures legitimate clean traffic reaches the original host server.


UDP flooder attacks are a modern, undetectable and growing problem with dire consequences when left unattended. Though such volumetric DDoS attacks cannot be totally eliminated, proper protection and safeguards ensure timely detection and take preventive/ corrective actions using Anycast technology and proprietary scrubbing software.

So, have you made up your mind to make a career in Cyber Security? Visit our Master Certificate in Cyber Security (Red Team) for further help. It is the first program in offensive technologies in India and allows learners to practice in a real-time simulated ecosystem, that will give them an edge in this competitive world.


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