Apple has announced a swathe of upgrades for its tablet, phone and computer operating systems that could change the way millions of people’s data is transmitted over the internet – a boon for privacy enthusiasts, but a potential problem for advertisers, law enforcement agencies and governments.

At Apple’s Worldwide Developers Conference yesterday, the company announced that upcoming updates to its web browser will offer an anonymous browsing feature called Private Relay. This will disguise user details from website operators by using a series of intermediary servers. Software to do this, such as the Tor network, already exists, but Apple’s move will make this kind of obfuscation far more mainstream.

The voice-recognition assistant Siri will also process audio on the device, rather than sending it to Apple servers for analysis, and changes to Apple’s email app will stop senders tracking when a message has been read and the IP address from which it was accessed.

The changes have provoked frustration from people working in marketing who track users to build up a profile and better target them. Matt Taylor, a product manager at the Financial Times, said that it will weaken the ability to provide advertising-supported services. He pointed out that around 50 per cent of email marketing is opened on an iPhone using the Mail app, so half of the data on users that was previously collected will be lost. (New Scientist, like most online publications, collects a variety of information about its readers.)