It's not just websites that track you when you're using a smartphone – apps also collect usage data. That's because companies make money with data collected from Internet surfers and smartphone owners.
"Some use the data for their own development, other companies offer it for sale, and others improve the user experience," according to web specialist Benjamin Lucks.
"To do this, they adapt search results and advertisements to the interests of the respective user," says the tech reporter.
The data business is the only source of income for many companies and users are now used to being able to use online services for free.
"Personalised advertising finances many free web services," says Martin Gobbin from consumer goods tester Stiftung Warentest.
"These are small snippets of data that help website operators to recognise users when they access a page," says online specialist Jo Bager from a tech news website.
Not allowing cookies on your smartphone or deleting them on a daily basis is one way to stop the bulk of personalised advertising on websites.
However, you cannot always escape other tracking such as IP tracking or fingerprinting – not even through so-called "anonymous tabs" or "incognito tabs", Gobbin says.
And yet there are browsers that not only prevent unwanted advertising, but also tracking. "On Android and iOS, there are free browsers with sophisticated ad blockers," says Bager, noting the Brave Browser (Android/iOS).
The Firefox mobile browser also blocks thousands of trackers by default. In addition, the Android version of Firefox allows you to install add-ons that prevent tracking such as Privacy Badger and Ublock Origin. However, you can't install add-ons in the iOS version of Firefox.
But what about controlling the data collecting by apps that you have installed or ones that were pre-installed when you got the phone? Many contain tracking modules, for example from advertising networks, which collect and send user and usage data.
This is where apps like Blokada come in, which monitors the smartphone's data traffic with the Internet.
By using filter lists and operating like a firewall, Blokada blocks communication with tracking servers, ensuring that data doesn't leave the phone. Users can also manually add any server address to a black list.
The full version of Blokada isn't available on the Google Play Store, but can be downloaded from the trustworthy F-Droid store.
Firewall alternatives to prevent tracking include the Netguard app, which can block all data traffic from apps, and NoRoot Firewall, which creates a virtual network connection (VPN) to divert all the traffic on your phone.
Firewall apps are also available on Apple's App Store, and one of these is Lockdown, which can block a connection to any domain and also gives the paid option of a VPN for additional privacy.
With a classic VPN, all of your own internet data traffic runs through a tunnel to the VPN service provider's server.
In this way, your IP address and thus the Internet connection and the geographical location are obscured. Third parties also can't see which pages are accessed or record the data traffic.
"The problem with VPN providers is that customers have to trust the provider that they actually keep their data to themselves," Martin Gobbin says.
For that reason you should be careful about free providers and also be aware of where their servers are based, for example in countries with less strict data protection laws.
It's also important to know that classic VPN services do not protect against cookies and other tracking technologies, nor data collection by social networks. – dpa
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