A DDoS attack is the the concentrated funneling of Internet traffic by a hacker against a particular website or server. In a successful attack, there's so much traffic on the site that its server(s) simply cannot cope and crashes under the strain of the data. Think of it like a massive online magnifying glass that burns unsuspecting servers like so many ants.

Back in 2011, these attacks made headlines when Sony's PlayStation Network went down, giving hackers access to millions of users' personal data. When Annonymous attacked Visa, Mastercard and Paypal, the attack was dubbed the beginning of "cyber rioting".