Using machine learning models and techniques, Google's Android Security Center removed more than 700,00 malicious apps in 2017, many of them apps that displayed adult ads to children or attempted to capture user devices to use as slaves in DDoS attacks.

Andrew Ahn, the product manager for Google Play, made the announcement, adding that 99% of harmful apps were identified and expelled before anyone could install them.

After placing all of its technology around malware scanning and detection under the Google Play Project last year, Google's operating system began to perform scans on installed apps. Users with Android devices can manually trigger scans on their phones via the updates section.

The measure came following the revelation that apps aimed at children were display ads meant for adults and that some copycat apps were exploiting device weaknesses to perform DDoS (distributed denial of service) attacks.

The quantity of apps removed in 2017 represent a 70% increase over the amount in 2016.

The most popular type of apps used to deceive users were copycat apps, with features, logos, and promotional copy similar to popular mainstays, often with fake or paid reviews, something Google is actively cracking down on.

Potentially harmful applications (PHAs) act as trojan horses for malware to phish a users’ personal information or commit SMS fraud by firing off texts without a user’s knowledge.

“While small in volume, PHAs pose a threat to Android users and we invest heavily in keeping them out of the Play Store,” Ahn said.