People's internet browsing histories including porn viewing habits and drug purchases can easily be bought online

The data is supposed to be anonymised. But in practice it's not at all

(Getty)

Your internet browsing history, including some of your darkest secrets, could be easily available to buy online.

Companies are gathering data on everywhere people go online and then making that available to buy cheaply. Most people are probably being tracked by the "clickstreams", which gather data using internet browsers about where people have been.

Researchers have showed that a German judge's porn browsing history and a politician's drug purchases were both easily found with data brought freely online.

Tracking users around the internet is intended to help with ads. By watching where people go online, marketers can target their posts – and then hopefully encourage them to buy things.

The data is supposed to be anonymised, and gathering such data is against the law. But it continues to happen and is sold easily online.

And it is easy for people to work their way around the anonymity and find out who the browsing histories belong to, the hackers told the BBC.

That could be done by simply using public data about what sites a certain person might have been to. By looking at sites people had publicly been to – such as YouTube videos they might have mentioned watching, or articles they shared on social media – they could be attached to specific browsing histories.

In some cases, the data included visits to specific personal social media pages, which meant that only the owner themselves could have visited it.

Two German researchers, Svea Eckert and Andreas Dewes, said that 95 per cent of the data they found came from 10 popular browser extensions. That means that anyone could be having their data collected in such a way and not know about it.