HSBC down: What is a DDoS attack, why are they so common, and how can you avoid one?

Sign up to our free weekly IndyTech newsletter delivered straight to your inbox Sign up to our free IndyTech newsletter Sign up to our free IndyTech newsletter SIGN UP I would like to be emailed about offers, events and updates from The Independent. Normal service is now being resumed and HSBC apologised for the outage, but the issues proved that even the most secure internet services are not immune to DDoS attacks. DDoS attacks happen so often because they're very hard to prevent - since the traffic comes from ordinary household computers, it's difficult for website owners to simply block certain machines from accessing their site, because they have no way of knowing whether the visits are legitimate or not. According to recent security reports, a DDoS attack that disables a website can cost as little as £25 an hour, although more major attacks like the one on HSBC would naturally cost more. DDoS attacks are practically impossible to prevent for most organisations, but companies like HSBC will have huge security teams trained to respond to such an attack and ensure that as little damage is done as possible.