Adrian Weckler: What is a DDoS attack? And why did it make several Irish government websites inaccessible?
A DDoS attack one of the most basic and common ways of bringing a website ‘down' without actually hacking into it.
It occurs when far more traffic than a website can handle is deliberately sent to that website to disable public access to it. If you think of a website as a revolving door, it would be like 100 people rushing to get through it at the same time: it would probably just stop letting people through.
The result is that the website becomes inaccessible to anyone trying to visit it.
The computing power is often marshalled by the aggressor using so-called botnets, which are clusters of computer servers that connect up and bombard a target with traffic it can't cope with.
This type of attack is what the Irish government is saying happened to websites such as those belonging to the Central Statistics Office (CSO.ie), the Courts Service (courts.ie) and the Department of Justice (justice.ie) on Friday morning.
This is not the same type of cyber attack as a hacking attack or a data breach attempt. Sensitive content is rarely accessed or stolen by the culprit responsible in this form of online aggression.
Culprits usually vary from activist groups such as Anonymous to pranksters.
DDoS attacks are becoming very common. One reason is that sophisticated tools to help launch DDoS attacks are very easily available online now.
In the last week alone, the websites of the National Lottery (lotto.ie) and Boards.ie have been hit by DDoS attacks. Three weeks ago, the BBC suffered one of the biggest recorded DDoS attacks in history.
It is generally difficult to trace the origin of a DDoS attack to find out who is responsible.
"We have implemented our contingency plans which are designed to minimise this disruption," said a spokesman for the Irish government this morning. "As with all DDoS attacks it is not possible to identify the exact source of the attack."