As smartphones have soared in popularity, app development has exploded. There are currently more than 3.5 million Android apps and games in Google’s Play Store, and more than 2 million apps and games in Apple’s App Store, according to App Annie. With such a feast of choice, people need a little help separating the wheat from the chaff.

App stores offer a review rating system for precisely this purpose. After you download and install an app, you can rate it out of five stars and write up a review detailing your thoughts. Review scores are aggregated and used to determine an overall score for the app. The higher the score an app gets, the more people liked it, at least in theory. In practice, a lot of reviews are less than useful for prospective installers and there’s a thriving trade in fake reviews. One star, one-line reviews complaining that an app didn’t work on this or that device, or that there was some billing issue, aren’t always a good indication of whether the app will meet your needs. But what about multiple five-star ratings with repetitive, unnatural-sounding reviews?

Gaming the system

Good review scores are vital if you want a coveted place in the app store charts. They boost your chances of appearing on curated lists and recommendations, and the bottom line is they can persuade people to install your app. Little wonder then, that some developers are willing to bend, or even break, app store rules to get closer to five stars.

“While we haven’t performed any specific analysis to quantify the scale of the problem, fake reviews do exist and have been shown to materially affect app review scores,” Paul Barnes, regional director at App Annie, told Digital Trends.

The fact that many developers game the system has been an open secret in the industry for years. A brief web search for “paid app reviews” or similar terms reveals several services selling app reviews and installations to artificially boost the standing of apps in the main app stores. While a small number of app reviews might cost $2 to $3 each, developers buying in bulk can secure discounts, with reviews costing below a mere 50 cents.

There’s no gray area here – this practice violates the Google Play Developer Program Policies and Apple’s App Store Review Guidelines. It can result in the removal of suspect reviews, the removal of the app, or even the expulsion of the developer from the program.

“Both Apple and Google have demonstrated they take the issue extremely seriously, and they continuously monitor reviews left on their respective stores,” Barnes said.

The problem is that determining what constitutes a fake review is easier said than done. Many of these services employ real users who download and install the apps and then post glowing reviews. While developers used to buy reviews in big chunks and post suspiciously similar write ups, things have gotten more sophisticated.

You can now dictate the wording of reviews, decide on post frequency, and stir in some four-star reviews alongside the five-star reviews to make it look more natural. Some of these paid app review services also guarantee they will replace any reviews that are deleted.

“We want ratings and reviews to be authentic and a true reflection of comments from the users,” Andrew Ahn, product manager at Google Play, told Digital Trends. “Spammy reviews, such as off-topic comments, solicitation, content with profanity, are just some of the categories we filter out. We also prohibit fake or incentivized reviews.”

Interestingly, the practice of buying reviews isn’t just about securing positive feedback for your own app — it can also be used to knock the competition down.

“There are two types of issues with incentivized reviews,” Ahn said. “One is buying good reviews to better promote your own app, and the other is buying negative reviews to harm competing apps. We cover both cases to keep the ecosystem clean and fair.”