What is a Denial of Service Attack?

Denial of Service

What is a Denial of Service attack?

A denial of service attacks is a form of cyber attack where a hacker aims to make a computer or network unavailable to its user.

It’s full description is described as a Distributed Denial of Service (DDoS) attack and is carried out by disrupting the services of a host that are connected to the internet by flooding the target with bogus requests which will overload the computer making it inaccessible by the users.

The UK is only second behind the US as being the most targeted country for DDoS attacks. The UK is subject to just under 10%of the world’s DDoS attacks, whereas the US boasts 50.30% of the total of attacks.

Over the last year DDoS attacks have increased by 211% as reported by cyber security consultants Imperva. The main source of the attacks is South Korea over taking China .

In recent months the size of attacks have started to become much larger. An average attack is around 200 Gigabits per second but attacks of between 600Gbps and 1 Terrabit per second are now evident. An attack of this magnitude would cause serious disruption to a businesses computer systems.

Consequences of a DDoS Attack

Business Interruption

A business could be severely disputed for a period of  time which prevents the business from trading normally.On-line retailers for example could loose a high volume of sales.

Reputational Harm

The business may suffer reputational issues following a DDoS attack and the perception by it customers that its cyber security procedures are not of a sufficiently robust standard

Common Types of DDoS Attacks

UDP Flood

User Datagram Protocol is where random ports are attacked on a computer system by packets which cause it to listen for applications on those ports and signal back with a ICMP packet.

Ping of Death

This is known as a “POD” that manipulates IP protocol by sending packets larger than the maximum byte allowance. As a result this causes the computer servers to crash.

Peer to Peer

This is where a peer to peer server is compromised to route traffic to a target website. Users are resultantly sent to the target website where it is eventually overwhelmed and is taken off line.


Dyn – The Largest DDoS Attack – Case Study 

This DDOS attack heralded a new dawn of what these forms of cyber attacks can achieve as it bought down a huge chunk of the US internet.

It was called the Mirai bonnet and targeted the servers of Dyn which is a company that controls a large proportion of the the DNS infrastructure.This occurred in October last year and took place for almost a day. In its wake it bought down household names such as Twitter, the Guardian and Netflix in Europe and the US.

A network of computers were infected with malware know as a “botnet” and coordinates into bombarding a sever with traffic until it gives way under the weight of the traffic that it is being hit with.

What was unusual with the Mirai botnet which normally consists of a number of computers but this consisted of Internet of Things devices that included digital camera and DVR players.

Due to the fact that so many devices connected to the internet this enabled the attack to be so much larger than any other previous DDoS attack. The attack was thought to be the strength of 1.2 Tbps and twice as powerful of  the next most powerful attack.

It is good business for hackers ….

Kaspersky Labs have carried out studies on Denial of Service attacks exploring the business model and its popularity. A DDos attack can costs as little as $7 an hour with the average rice being $25 an hour . The profit margin can be as much as 95%.


Cyber Insurance 

Cyber Insurance can provide assistance in the event of DDos attack by providing the following policy coverage :-

Business Interruption

Cyber Extortion

Incident Response Services

Businesees need to be prepared for the threat that a DDos attack can bring and it important that their cyber security risk management procedures are effective to combat attacks of this nature which are being bought about with increasing severity by hackers.

Image : Shutterstock