You must have heard from a tweet or a Facebook status update or God forbid a conversation, that Oren Peli’s debut film, “Paranormal Activity,” is actually a decent scary movie. Perhaps you heard it less elaborately or with more exaggeration, but it came, nevertheless, by word of mouth.

This sort of viral marketing strategy was what got Paramount Pictures and DreamWorks SKG’s “Paranormal Activity” over one million demands for a nationwide release after being strategically screened in college towns at midnight guerilla-style showings. Thereafter, the film’s trailer showed up anywhere from computer screens to television sets with a URL where you could vote to have the film come to a theater near you.

The film’s benefactors were more than happy to supply a nationwide release of a movie with a budget that doesn’t even cover the cost of an average college tuition. The mockumentary of a suburban San Diego couple experiencing bumps and whispers in the night picked up momentum with a reputation that leveled it with the decade-old “The Blair Witch Project.”

The comparison is fitting. The film’s psychological thrill is in its pseudo-realistic, lo-fi film quality, making it seem believable that the film is really made of compiled homemade tapes, that the characters are real people, and that whatever they’re seeing or hearing is real and could even happen to you.

But before it’s national October release, the movie had already been ghosting around in small indie film festivals such as Slamdance and the 2007 Screamfest Horror Film Festival, where it got an honorable mention. It eventually haunted its way to the attention of Paramount and DreamWorks SKG; needless to say it impressed and was sold to Steven Spielberg.

Spielberg, a long time influence on Peli, saw the movie and suggested a replacement of actors Katie Featherston and Micah Sloat with more famous faces along with a new ending. However, Spielberg’s suggestions were rejected, keeping the film’s style and credibility as a possible real-life event intact. And that is what audiences go home to their computers to discern: “Did this really happen?”

Sort of. The film’s screen writing came from Peli’s own experience living in a house with his then-girlfriend Toni Taylor. The couple, like Micah and Katie in the movie, started hearing noises, finding things had been moved across the room, and felt shaking in their bed. Peli decided then and there that a hyperbolic dramatization of those events would fulfill his giddy filmmaking itch and may even do well in theaters.

By September, the film was already getting murmurs among young audiences. Movie reviews helped skyrocket the film’s popularity with loose plot-summaries and a promise, on occasion, to not let you sleep at night.

The film’s thrill relies on anticipation, silence and abrupt thuds. A skeptical audience turns into stubborn believers when they watch first-hand as doors close, things catch on fire, and sheets puff up in the still midnight air. Audiences nationwide have and will continue to walk away in some form of shakiness or fear.

Is it the best horror film? Arguably. Will you squirm and scream? Perhaps. You won’t know for sure until you’re there. After all, seeing is believing.