Before smartphones, most people’s experience with operating systems was from computers. Naturally, many of those desktop habits carried over, and malicious Android developers were more than happy to take advantage.
The early Android Market—now the Play Store—was full of “task killer” apps. These apps promised to make your phone feel faster by killing background activities and freeing up RAM. They were extremely popular and also extremely unnecessary. Several of the well-known apps in this genre, including those from one particularly infamous developer, were running scams.
How Android task killers preyed on the uninformed
Android doesn’t work like a desktop OS
There are several valid reasons why Android task killer apps were so popular in the beginning. First and foremost, it just seems like the logical thing to do. On computers, we click the “X” to close apps when we’re done with them. Why would I leave an app running in the background if I’m not using it?
The other thing working in task killers’ favor was the performance of the first Android phones. They were limited by much less RAM than we enjoy today, low-powered processors, and worse battery life. Naturally, people were looking for any possible method to extend their devices.
Sadly, when people are looking for answers, it’s not uncommon for nefarious actors to step in with “solutions.” That’s exactly what happened when a popular flashlight app was caught selling user data. Similarly, several task killer apps were not as benevolent as they seemed.
Clean Master and the magical “boost” button
Placebo in action
Not all task killer apps were frauds. Many of them genuinely did kill processes in the background—for better or worse. However, a few notorious apps were caught doing much worse. Cheetah Mobile’s “Clean Master” is perhaps the most well-known.
Clean Master first arrived in the Play Store around 2012, and it quickly became a popular choice for those looking to speed up their Android devices. The app billed itself as the “CCleaner of Android”—a mega-popular Windows app—and at its peak, it had over a billion downloads. Here’s the app description from 2013:
Clean Master is an all-in-one cleaner app on android for cleaning app cache , unused files, residual files, search history and uninstalling apps. With this apps user can also Kill running Tasks and releases more RAM to boost your phone performance and save battery life without granting superuser permission. Just think of Clean Master as the CCleaner of Android.
By 2014, Clean Master had also added antivirus to its list of features, but the “Memory Boost” was the crown jewel. The app would show you how much of your device’s RAM was being used and let you clear it out by tapping the “Boost” button. You might see “54% used” and watch it go down to 0% in an instant. How good does that feel?
Unsurprisingly, not all of this was magic was real. Clean Master had legitimate features, like the ability to uninstall apps and clear cache files. Clearing the phone’s memory, however, didn’t actually help anything, but that’s not what got Cheetah Mobile in trouble.
Cheetah Mobile gets caught red-handed
Deceptive ads and click fraud
The first news of Cheetah Mobile’s less-than-stellar practices came in 2014. A researcher from Sophos Labs, a British software security company, discovered that Clean Master inserted pop-ups when people were browsing websites inside Cheetah Mobile’s ad network. These pop-ups told people their device had been infected with a virus, and pointed them to Clean Master as the solution.
For their part, Clean Master blamed its advertising partners and promised to identify the problem and fix it. The app remained in the Play Store unchanged.
Four years later, in 2018, Cheetah Mobile found itself at the center of a much bigger controversy. A researcher at Kochava, an app analytics company, found eight Android apps in the Play Store that were exploiting permissions as part of an ad fraud scheme.
Seven of those apps were owned by Cheetah Mobile.
Under normal conditions, when a user installs an app from an ad, the publisher of that ad gets paid. After installation, the app does a “lookback” to see where the last click came from—i.e., the ad. Cheetah Mobile was inserting itself in this process, making it look like they served the ad and, therefore, should get paid.


Cheetah Mobile voluntarily removed two of its offending apps, but Clean Master remained in the Play Store. It wasn’t until 2020 that Google finally took action and removed over 600 apps, including Clean Master and the remaining Cheetah Mobile suite. By this time, Clean Master had amassed over one billion installs and 45 million reviews—it was rated 4.7/5.
Be wary of unnecessary apps
So, what’s the moral of the story here? Clean Master technically did some of the things it promised, and users were not directly affected by the company’s sketchy tactics. However, they were clearly used against their will to make money for Cheetah Mobile.
Nowadays, most people understand that Android manages all of this stuff for you. Apps are automatically put to sleep when their resources are needed elsewhere. The OS also has tools in place to keep rogue apps in check. Plus, hardware is simply much better. We have plenty of RAM, powerful processors, and much-improved battery life.
Still, it’s a good reminder that you should be skeptical of any app that claims to do system-level tasks with the tap of a magical button.
Shining a light on a shady app.





