Virus alert!

"Seen this yet?" As an email header it doesn't say much, but for a generation hooked on the in-work distractions of viral advertising, these three words are manna from heaven. The concept of viral marketing - peer-to-peer advertising where the consumer does all the work - first cropped up in the late-90s and, over the past decade, has spread like, well, a virus.

The big idea is that a generation of consumers in love with technology and raised on the internet, MTV, multiplex cinema and The Fast Show, lack both the attention span and inclination to consume traditional media and so had to be reached in a new way. That way was the viral.

Short enough to appeal to the butterfly concentration span of the average teenager and low enough in bandwidth to be passed around from mobile phone to inbox to PDA, the viral has become the defining advertising medium of the early 21st century. So much so, in fact, that it has already become a key tool of both Democrat and Republican campaigners in this year's US presidential battle.

While this may indicate that viral advertising is already nearing the end of its shelf life, the medium is likely to mutate. Until that happens it remains the advertising industry's favourite concept and the number of virals produced either as standalone statements, tag-ons to bigger campaigns, or just as a statement of subversive mischief, continues to grow.

One of the best currently cluttering up inboxes throughout the UK is digital design agency AKQA's masterful Pot Noodle spoof of the expensive Nicolai Fuglsig domino-toppling Guinness ad. The sting in the tail of the short After Effects-powered spot, though, is that instead of an Argentinean mountainside, the action is relocated to a gritty North London council estate.

"The Guinness ad is good, but I knew that by bringing it closer to home we could go one better," says Allan Little, brand development manager for Pot Noodle. "Their dominos only went downhill - we've got some that go up steps."

The spoof viral features real people living on two estates, going about their day-to-day business. The objects in the viral's domino chain include cigarette packets, mobile phones, a wheelchair, white goods and supermarket trolleys.

Directed by AKQA's Dom Bridges, the viral was put together through collaboration with the local community living in the estate. As the blogs are saying: "Genius!"

Like AKQA, digital agency Ralph is another company that has surfed the creative viral wave over the past few years and has been involved in creating some of the most stunning examples of the art form. Currently running a project for Paramount Pictures to promote horror film The Ruins, Ralph was approached by the movie giant to come up with a way to promote it. "Our idea involved broadcasting a guy live on webcam, showing people a vine growing in his arm after an accident he had in Mexico," a Ralph spokesman says.

The company's Ruins viral has immediately picked up a massive following attracted through the classic viral word-of-mouth buzz about the weirdness of the site.

Ralph is also the name behind a recent viral promoting a new series of hit thriller series Dexter. The viral campaign is based around a fake US news report about a serial killer on the rampage, to which visitors can add information about their friends. Recipients receive a link to a spoof video viral website that features the fake US news report about the serial killer.

Over in the US at the moment, virals are ably demonstrating the tightrope that brilliant campaigns can easily walk between success and failure. One such viral is a Jack Nicholson-starring endorsement of Hillary Clinton put together by the ex-First Lady's campaign team, featuring clips from some of Nicholson's best-known films and built around a simple message: Who do you trust?

Only days after the viral began doing the rounds, a Barrack Obama-backing version hit the nation's inboxes. This neatly subverted the original, making a more memorable statement letting Hillary know "the opposition was closing in".

Pete Brown, from viral treasure chest BoreMe.com, says: "Jack Nicholson's 'Who do you trust' message for Hillary Clinton was easy to reverse. People will remember the spoof rather than the original - that's the risk."

Viral advertising is having its heyday. How much longer it will last is anyone's guess. For now, though, it's back to check what's turned up in the inbox.