Apple Inc.'s App Store is coming up on its fifth anniversary. To celebrate, the company has introduced the "Five Years of the App Store" section offering some of the most popular paid apps for free. Meanwhile, it contains a timeline of specific milestones in the App Store's five year history. At its World Wide Developer's Conference, Apple CEO Tim cook said the store had "fundamentally changed the world." However, a number of the apps on the market go mostly undownloaded and become "zombie apps."

With the App store boasting 900,000 products has left many developers struggling to get noticed. BBC News reports U.S. analytics firms known as Adeven claims 579,001 of these apps are "zombies" or, apps that go largely unnoticed by the public and thus are almost never downloaded.

It defines zombies as apps that never appear in Apple's master-list of the most downloaded apps worldwide, a chart that runs to over 300,000 places.

Apple doesn't give out information on how many times these apps are actually downloaded, but Adeven says the numbers are significantly low.

App developer Malcolm Barclay told BBC News the amount of zombie apps was not a surprise, he feels the App Store still works as a result of safety in numbers.

"There's a lot of apps in the store that are not downloaded for good reason, they're awful," he said. "It's about making yourself attractive. If you have an attractive application that does what it sets out to do, Apple will help it get noticed."

There is some credence to this theory, Adeven's research determined 68 percent of smartphone owners used five or fewer apps each week. Many of the others purchased end up phasing out of the user's iPhone or Android device simply because they were impulse buys made while browsing the app store that don't have any real staying power. With these downloads, visibility was the key in at least giving it a shot.