Spotify, as it gears up to go public in an IPO expected later this month, is disabling access from unauthorized Android apps that let users circumvent advertising and usage restrictions from free accounts.

Spotify’s free accounts serve up ads between tracks and disallow on-demand playback on mobile devices (and mobile users also are limited to skipping a song six times per hour). The illicit apps hack the Spotify service to bypass those limits, to provide features available in Spotify Premium, which costs $9.99 per month.

Over the past several days, Spotify has been alerting users that their access from such hacked apps is being disabled — and it’s warning them that their accounts may be shut down if they continue to use such third-party apps, as first reported Monday by piracy-news site TorrentFreak. A Spotify rep confirmed that the company has sent the notices to applicable users but was unable to provide info about how many users were sent the warnings.

The notifications read: “Dear user: We detected abnormal activity on the app you are using so we have disabled it. Don’t worry — your Spotify account is safe. To access your Spotify account, simply uninstall any unauthorized or modified version of Spotify and download and install the Spotify app from the official Google Play Store.”

Popular on Variety

The message concludes, “If we detect repeated use of unauthorized apps in violation of our terms, we reserve all rights, including suspending or terminating your account.”

As of the end of 2017, Spotify reported 159 million monthly active users total, and 71 million paying premium subscribers.

The company generated nearly $5 billion in revenue in 2017 (4.1 billion euros), versus $3.6 billion in 2016. Its operating loss for 2017 was $461 million, compared with around $425 million in 2016. Spotify started in Stockholm, Sweden, but its official corporate headquarters is in Luxembourg.