Hackers paralysed the popular micro-blog website Twitter and forced it offline for more than two hours on Thursday morning.

The California-based site was struck by a ‘denial-of-service’ (DoS) attack. People who carry out DoS attacks can command hundreds of computers infected with viruses to visit a website at the same time. The simultaneous visits often overwhelm the website servers, and slow down service or even force it offline.

Twitter has become enormously popular in recent months. Users can access it via the internet, or their mobile phones, to post short messages of no more than 140 characters.

The social networking site Facebook said it had also suffered from a DoS attack on Thursday and that its service had been “degraded’.

Twitter icon by mfilej (flickr)