Governments monitor smartphone users through push notifications in apps. This was warned by U.S. Senator Ron Wyden, according to Reuters.

In his letter to the U.S. Department of Justice, he stated that foreign officials were demanding data from Google and Apple.

Push notifications inform smartphone owners about incoming messages, breaking news, and other updates. However, users often don’t realize that almost all such notifications go through Google and Apple servers.

According to the politician, this gives the two companies unique information about the traffic coming from apps to their users and puts them “in a unique position to facilitate government oversight of how users use certain apps.”

With this in mind, he asked the Department of Justice to “rescind or modify any policy” that prevents public discussion of spying through push notifications.

In its statement, Apple noted that the letter from the US senator gave the company the opportunity to share more information with the public about how governments monitored push notifications.

“In this case, the federal government prohibited us from sharing any information,” the company said in a statement. “Now that this method has become public, we are updating our transparency reports to detail such requests.

For its part, Google shares the US senator’s desire to inform users about these requests.

Earlier, French developer David Libo said that users and developers are often unaware of how their apps share data with US tech giants via push notifications, calling them a “privacy nightmare.”