European governments from the nineteenth-century started putting numbers on houses and flats. Long before there was CCTV, this was and early attempt by the state to monitor its citizens. The shape of city was beginning to take shape in map form. Then, at the beginning of the twentieth-century, with the explosion of the car industry, the road map emerged. These were often printed courtesy of oil companies to encourage motorists to use more petrol.

The history of the map has always gone hand in hand with the exercise of power and control. It also functions as a safety net against a creeping void that threatens to encompass the city. In 1952, Chombart de Lauwe mapped the movements by a student living in the Paris. Her itinerary formed a small triangle with no significant deviations, the three apexes of which were the School of Political Sciences, her residence and that of her piano teacher. She too was keeping the void at bay.

But on ground-level, counter-insurgents have persistently tried to reclaim the city, fusing the map with abstract geometries, reprogramming the curvatures of the landscape in algorithmic computer code or compsing insurrectional instruction manuals on brick walls. Passing under the eye of CCTV cameras, shadows in the orange-glow of street lights, evading police and marauding gangs, these characters make sacrifices to the city’s godheads, messages rich in mysterious symbolism. From household goods dumped on street corners, abandoned shopping trolleys, graffiti, and empty rucksacks left by lone thieves in the night, these are communications from another reality, attempts to open up a space for the spirit world. But before the sun rises and the city returns to work, all traces of these offerings are washed away by council services with their power-hoses and bin-lorries.

It’s against this backdrop that the work of Invader has spread, from Paris and then across the rest of France, to Amsterdam, Dhaka, Istanbul, London, Los Angeles, Mombasa, New York and Tokyo. His delicate mosaics are placed at specially-chosen spots –it varies from buildings to monuments to bridges to park fences – and together they form a net which has the city covered. The Space Invaders are cracks in the code, jamming signals, white blood cells amidst the swarms of Starbucks Coffee dividing and multiplying in our cities, and the infection of ‘Time Out Recommends’ stickers in the glass fronts of restaurants, which like a flag planted in the soil announce ‘We got here first’.

The Space Invaders are not signs telling you walk on the pavement, to look right, look left; they’re not state-legitimated billboard advertising, they’re not injunctions to drink here, eat there, and drop your Mastercard, Amex or Visa. They appear overnight in your neighbourhood, keeping a watchful eye over the city that never sleeps.

The mystery surrounding these Space Invaders has led to rapid speculation. Are they signs from outer space, warning of the imminent destruction of the planet? Are they adverts from sophisticated criminal cartels pushing memory-erasing drugs? Subliminal messages poisoning the minds of children? Or do they monitor latencies and potentialities imperceptible to the human eye, like occult speed-cameras?

Despite what they say, Invader reassures us that there’s nothing untoward in his mission. “I’ve heard many rumours about my work,” he says, “but actually the one I hear the most is that it’s a group of us putting up Space Invaders around the world, which is not true. It’s just me, and this has been my main activity for the past 10 years – always on the move, travelling across five continents and 40 cities where I’ve created thousands of Space Invaders. People have said that I must be either autistic or an obsessive-compulsive, but I believe it’s been necessary for this project to work.”

Using mosaics (a visual form that dates as far back as the ancient Sumerians) to recreate characters from the halcyon age of arcade games, Invader’s work opens up a short-circuit in time. The pixel, base element of the computer revolution which gained momentum in the 1980s with games like Space Invaders and the first generation of home computers, began millennia ago with the mosaic. It’s black hole, a loop in time opening up between civilisations and realities.

What’s more, with the epidemic of Space Invaders unleashed on the city, the artist’s project becomes an urban hacking realitygame – a video game executed in real life where the boundary between lived experience and the gamesphere becomes increasingly fluid. He awards himself points for each mission and he’s passed the 100 mark in Paris and Los Angeles (15120 points and 2450 points respectively), while in London and New York he’s just shy of this score. He still has some way to go, however, before he beats Eric Furrer’s total (Furrer is the world record holder for the Space Invaders arcade game, playing the same game for 38 hours continuously).

The street artist shares something with the video-gamer, insomniac communities staying up until the break of dawn, waging wars-with-no-name. Says Invader, “I’m always having weird or unexpected encounters while I’m out invading. It’s an inescapable part of working mainly through the night in cities across the world. The people up at night are marginals, it’s a totally different universe. I love the saying that Shepard Fairey (Obey Giant) came up with – ‘While you were sleeping, we were bombing’”.

It’s ideological warfare on street-level. In Chris Marker’s film Sans Soleil (1983), the filmmaker goes out to Japan and remarks of the video arcades, “I’ve seen young Japanese exercising their brain muscles like the young Athenians at the Palestra. They have a war to win. The history books of the future will perhaps place the battle of the integrated circuit with the same levels of the battles of Salamis or Agincourt.”

Before hitting the city, Invader’s first sorties included sabotaging video cassettes. “I used to hire videos from my local video store and would overdub subliminal images of Space Invaders onto the tapes,” he explains, with a wry smile. “I’ve invaded hundreds of videos over the years. The idea was to find subversive and unexpected ways of staging invasions. With the arrival of DVD’s, it’s not so easy to do anymore.”

From video cassettes to the street, his invasions have been spreading like a virus – mind bombs lying in wait for unsuspecting pedestrians in the city who momentarily let their eyes wander. His feats have become more and more daring, targeting the Louvre in Paris in the 1990s long before Banksy pulled off his stunt at the Tate. Then on 31 December 1999, as part of his Los Angeles invasion, he bypassed the high-security chain-link fence and a slew of CCTV cameras and placed an Invader Millennium Bug on the D of the giant Hollywood Sign.

He’s also collaborated with fellow Frenchman Zevs (whose exploits famously include replacing police car number plates with designs of his own) and together they’ve created posters, videos and games under the @nonymous moniker. Their attack on the southern city of Montpellier left a trail of targets which, when viewed on a map, formed the shape of a Space Invader. Logging and photographing his incursions is an integral part of Invader’s project, and he has subsequently released a series of maps for each city he’s targeted, like an alien guide to the city.

While he’s attracted fans across the globe, there’s also the inflitrators who have been following the maps and systematically removing the mosaics with a hammer and chisel. In Los Angeles especially, double-agent crack teams went around wiping out all traces of the invasion. Returning to the sites where his pieces have been defaced, Invader’s been known to stencil ‘10 Points’ next to the ruins.

But if Invader seems like just another graffiti artist, the truth is that it’s only latterly that he’s begun to make links with the squads of French taggers and US street artists like Shepard Fairey who he describes as “someone I was both surprised and happy to meet, someone on the other side of the world working in the same direction as me”.

There’s a whole other history to street art, the unwritten version, one that doesn’t begin in the Bronx with Wild Style, but instead one that’s borne out of the revolutionary events on the Left Bank of Paris in May 1968. Inspired by Guy Debord whose situationist drifts across Paris would include writing messages in chalk across the streets of the capital, a generation of French students covered the walls of Paris in revolutionary slogans, ranging from naïve messages like ‘fuck the system’ to the wilfully obscure to inspired and insurrectional street poetry.

“I feel very close to the Situationists who perfected the art of wandering through cities. It’s exactly what I do when I invade a new city. I pass through streets I’ve never travelled before, keep my eyes peeled, and I’m always discovering new things. There’s no precise rules when it comes to placing the mosaics – it’s something completely subjective. Sometimes I feel like a spot calls me, I feel like I should place a piece there, and from there I do everything in my power to reach this goal. Each invasion is an intense experience, a protracted stealth attack spun out over several weeks.”

In the latest phase of Invader’s work, he’s been recreating iconic images – from the Mona Lisa to A Clockwork Orange – using nothing but Rubik’s Cubes. An extension of his fascination with the pixel, his Rubikcubism has to be seen to be appreciated. Each image he recreates is assembled from hundreds of these Rubik’s Cubes. And there’s no question of peeling off labels. Each Rubik’s Cube is twisted and turned until its 9 pixels match the image he’s trying to represent. It’s a labour of love and an extension of Invader’s obsessive approach to his art.

As he increasingly tours gallery spaces and launches more books – his Invasion London is published this year, and is a follow up to L’Invasion de Paris (2003) and Invasion Los Angeles (2004) – this artist seems to be moving from the street to the gallery space. Yet his Space Invaders remain out there, skylarking on street-corners, lying in wait in dark alleyways or perched on bridges. They’re spirits of the data-city, talismanic symbols completing the loop between ancient and future metropolises, between the soul and the circuit-board. Hijacking the urban map from the clutch of the motor car, twisting the two-dimensional reality of Google Maps and GPS systems into examples of symbolist poetry, the Invasion goes on… Ignore it at your peril.