What are DoS and DDoS attacks?

If your favourite website is down, there’s a chance it’s suffering a Denial of Service (DoS) attack. This is more likely if the site is an online shop, a bookie or another site that relies financially on being online at all times.

Enemy at the gates
A DoS attack tries to make a web resource unavailable to its users by flooding the target URL with more requests than the server can handle. That means that during the attack period, regular traffic on the website will be either slowed down or completely interrupted.

A Distributed Denial of Service (DDoS) attack is a DoS attack that comes from more than one source at the same time. A DDoS attack is typically generated using thousands (potentially hundreds of thousands) of unsuspecting zombie machines. The machines used in such attacks are collectively known as “botnets” and will have previously been infected with malicious software, so they can be remotely controlled by the attacker. According to research, tens of millions of computers are likely to be infected with botnet programs worldwide.