A Denial of Service attack (called a DoS attack) is aimed at preventing or blocking access to a server or a website. Hackers achieve this by overloading or terminating a service, and generally, no data are stolen or damaged. To you as a user, it is more a case of a nuisance, as you will not be able to use the service (e. g. e-banking), for a period of time.
- using up-to-date antivirus software
- having a firewall activated
- regularly installing updates for your operating system and all the software installed
- always remaining careful and alert
There are different types of DoS attack. The most common involves simultaneously sending very large amounts of data to a service on a server so that it becomes overloaded and is unable to reply to any further queries (e. g. the website is no longer shown in your browser). Such large data quantities are usually sent out using a botnet (see below). This is then called a Distributed Denial of Service attack (DDoS attack).
Attack from a single computer (DoS – Denial of Service)
A DoS attack is carried out directly from one attacker aimed at one victim. No other computers are involved. The attacker uses his own computer to attack.
DoS attacks are quite rare nowadays, as it is quite easy to trace them back, putting any attacker at a certain amount of risk of quick discovery.
Co-ordinated attack by several computers (DDoS - Distributed Denial of Service)
A DDoS attack is split into two steps. During the first step, the attacker takes over several computers on the Internet using a Trojan or some other malware, building a so-called botnet. During the second step, the attacker then takes control of the infected computers (the botnet) and makes them all attack his target (e. g. a certain website) at the same time.
A DDoS attack is very effective, as it is run from a great number of computers at the same time, so that it is very easy to generate the large quantities of data needed. This type of attack is generally used to paralyze servers and websites. With DDoS, it is usually difficult to establish the actual originator of the attack, as the attacker's computer does not attack his target itself.
It is very important that you adhere to the «5 steps for your security» so that your computer doesn’t become part of a botnet and an «involuntary participant» in a DDoS attack this way.