The updated Google Play policy, announced last month, will take effect on November 1. It states that only apps using the Android VPNService base class, and that function primarily as VPNs, can open a secure device-level tunnel to a remote service.

Such VPNs, however, cannot "manipulate ads that can impact apps monetisation."

The big idea is to deter data-grabbing VPN services, such as Facebook's discontinued Onavo, and to prevent ad fraud, but Blokada, a Sweden-based maker of an ad-blocking VPN app, worries this rule will hinder at least the previous iteration of its software, v5, and other privacy-oriented software.

 Reda Labdaoui, marketing and sales manager at Blokada said: ""Google claims to be cracking down on apps that are using the VPN service to track user data or rerouting user traffic to earn money through ads. However, these policy changes also apply to apps that use the service to filter traffic locally on the device."

Labdaoui suggests Blokada v6, which launched in June, should not be affected because it does filtering in the cloud without violating Google's device policies. But other apps may not be so fortunate.

The DuckDuckGo Privacy Browser for Android, creates a local VPN service to make its App Tracking Protection block tracker server connections, as a potential casualty of the new Play policy, he claimed (although DuckDuckGo was certain it will not be impacted by the policy change).

Another app that could be affected is Jumbo for Android, which also appears to use VPN-related code to block trackers.

To be fair Google's policy follows Apple's iOS App Store which also requires the use of NEVPNManager, which is available only to developers who are part of an organization, not unaffiliated individual developers.

The iOS rules state, "You must make a clear declaration of what user data will be collected and how it will be used on an app screen prior to any user action to purchase or otherwise use the service. Apps offering VPN services may not sell, use, or disclose to third parties any data for any purpose, and must commit to this in their privacy policy."

This means that Apple could ban an iOS app that interferes with the functioning of other apps.

Google for years has disallowed Android apps that block ads in other Android apps (with the exception of browsers), and its Chrome Web Store includes language that could be used to ban ad blocking extensions if Google chose to do so. For example, "We don't allow content that harms or interferes with the operation of the networks, servers, or other infrastructure of Google or any third-parties."