Apple has revised its app-submission rules to help block scammers who submit an app for approval, then later upload fake screenshots or alter descriptions to make the software appear to be more fully featured than it really is, or even a clone of another, well-known app.

In a developer note titled "Updating Screenshots in iTunes Connect" posted Wednesday, Apple said that "app screenshots will be locked in iTunes Connect once your app has been approved," and that the change is effective immediately. "New screenshots may be uploaded when you submit a binary for an update to an existing app or a new app."

The change affects all book, music, TV show, movie and app sellers, across iTunes Direct, the App Store, iBookstore and Mac App Store.

Bait-and-switch scams are commonplace in the real world, for example in restaurants that advertise one type of wine but replace it with a cheaper substitute, or via emails that promise free iPads, but simply lead to endless online surveys. "But switching out an actual application in the iOS world is much harder, because Apple vets each app first, then digitally signs it and only then makes it available for download," said Paul Ducklin, head of technology for Sophos in the Asia Pacific region, in a blog post. "Nevertheless, you can still run a scam, even with vetted and digitally signed apps."

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Indeed, over the past year, multiple scammers have submitted an app to Apple, gotten it approved and then later altered the screenshots or listing details. In February, for example, scammers placed a clone of Nintendo's "Pokemon Yellow" game in the App Store. They sold an unknown number of copies before users complained and Apple yanked the application, reported iOS gaming site TouchArcade. The scammers knew their target market well: Nintendo doesn't sell any apps via the Apple App Store, which would have made the app immediately attractive to Pokemon fans.

The Pokemon app was completely non-functional, reported TouchArcade. Even so, "people have been scrambling over the thousand or so one-star reviews in order to give it a spin," it said at the time, noting that it quickly became the third most popular paid app. "Money is being made here, and it's the significant variety," said TouchArcade.

Another scam, meanwhile, involved Minecraft clones, including one titled "Mooncraft." Scammers apparently "used different screenshots to get past Apple reviewers, and then later changed the game information," substituting actual screenshots from the real Minecraft game, reported MacRumors. It noted that Apple, in the past, has reimbursed people who purchased scam apps.

Why scam iOS app buyers? Given the number of people who download iOS apps, attackers could arguably turn a quick profit. On the other hand, Apple only pays developers once per month, meaning that a successful scammer would have had to game not only Apple's app-approval process, but also payment timetable.

Still, those hurdles haven't deterred every would-be scammer, which led Ducklin to praise Apple's changes. "Looks like this particular bait-and-switch game is up. Good," he said. "Of course, one wonders why Apple, a company that is so punctilious about the actual software it lets into the App Store, hasn't enforced a corresponding precision in App Store advertising all along."

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