Viral films are short catchy videos with a concise message. They get distributed by emailing, instant messaging, links to websites (YouTube for example), or people ‘embedding’ them in their blogs.

They spread in much the same way as human viruses do – from person to person. But unlike viruses, which are rarely welcome, more and more people (especially young ones) love finding the best virals, and passing them on.

There are rules, though. They need a good hook (like humour, a sexy element or an unexpected twist) so that people feel compelled to send them on. They also have to be short – normally two minutes at most.