If you had lived in East Germany between 1950 and 1989 it is quite likely that the State Security Service, known as the Stasi, would have kept a file on you.
Right up until the fall of the Berlin Wall some 91,000 people were employed full-time by the organisation, and at least 170,000 worked – sometimes unwillingly – as informants.
The Stasi kept files on 6 million citizens, about one third of East Germany’s total population.
At its peak it had become the most widespread and comprehensive surveillance operation in history.
But the information they laboriously collected through wiretaps, hidden microphones and intercepted mail seems tame in comparison to the data harvested and processed by the likes of Google and Facebook today.
On the surface the comparison seems overwrought, and perhaps in poor taste.
Our favourite tech giants do not interrogate or blackmail their users under the threat of imprisonment or worse.
Instead we willingly give up our personal information, and betray our secrets, in return for access to services that are useful and free.
But the extent of the information these internet giants collect still has the capacity to surprise.
If you are one of Facebook’s 2 billion active users – or a user of one of the services they own, like Instagram or WhatsApp – then at any given moment it is possible they know where you are, what you are doing, and who you are with.
This comes not only from your activity on Facebook-owned services, or your visits to the millions of websites with an embedded Facebook tracking pixel, or the sensors and location services on your phone.
It also comes from the information Facebook buys from data brokers, including credit reference agencies and supermarket loyalty schemes, so they can build an incredibly detailed picture of your life.
This is all designed to enable advertisers to better target you when you are most susceptible.
For businesses it is an incredibly powerful way to find people that might be interested in specific products and services.
And, as the most recent US election has shown, it might also be a useful way for the modern-day equivalent of the Stasi to influence voters.