A day without data

Every day, anyone who is connected to the internet leaves an ever bigger trail of data behind them. But how aware are we of who is collecting this information and of who benefits from it? I spent a day without data to to explore these questions.

My guide for this no-data diet is Dr George Danezis, an expert on privacy and information security at University College, London. As I sit at the breakfast table, handing over my gadgets he sets out the challenge I face:

"Your job today is going to be very difficult, You won't be able to use the internet, but you also won't be able to do lots of other things - in fact you won't be able to live a 21st Century life."

As someone who is addicted to being online, checking Twitter the moment I wake up, still reading online news last thing at night, giving up my smartphone is hard.

But George also makes me hand over my travel card and my BBC identity card which gets me into my office. Both record data about my location, so they have to go.

Even dogs can have a data trail if they're chipped

George explains that there are three big collectors of data: companies, governments and the police and the security services. Consumers may have grown accustomed to this data collection and in some cases see benefits.

But we may still be in the dark about some aspects. "It's collected for primary but also secondary purposes, you might be handing over data while you're shopping and that might be used later for marketing or working out health insurance."

I determine not to buy quite so many biscuits if that is going to send bad signals to my insurance company.

We head out with the dog for a walk, trying not to leave data as we go. George explains that we could not take the car without the risk of being tracked, either by my satnav or by number plate recognition systems.

And of course in London a bus is also out of the question - the drivers no longer take cash, only London's Oyster card.

Without my mobile phone, which constantly tells the network operator where I am, I should be safe just walking along, but then George points to the various CCTV cameras monitoring our progress along the High Street.

Using cash is no guarantee that your purchase cannot be tracked

Even a trip to the shops with cash rather than cards presents difficulties. "Big notes have their serial numbers tracked by the banks. If you take one out of the cash machine and give it to the shop they will pay it straight back into the bank and then you can be tracked."

I ask George whether I might be better staying at home. For now, he says, that might be okay but what about when my home becomes smart?

"Right now you assume your kettle isn't sharing data but smart objects will be much more difficult to read. You might pick up some object that looks innocuous, like a kettle, and find out that it does actually share information."

We end up taking the dog for a walk in the woods. Surely here, far from CCTV cameras, mobile phones, smart cards, I am off the grid? But George points out that even Archie the dog is chipped, so in theory someone with a reader could work out where his owner is.

And, just as we dismiss that as totally far-fetched he comes up with something more unsettling.

"If someone like you who normally shares a lot of information suddenly goes totally dark, this in itself is quite noticeable and a lot of analytical systems out there will immediately notice that something odd is going on."

Once you have laid a data trail, it seems, even going off the grid does not work.

But having thoroughly unsettled me, George tells me not to be paranoid and gives me some tips for healthy data habits.

"There is a good reason to keep track of public policy around data - make sure that no more than necessary is collected. You should also make sure that the technology you have has options for being used without collecting data, which as we've seen today isn't easy."

Maybe we should all read those endless privacy statements from online companies instead of just pressing "Agree". Or perhaps it is time for consumers to demand more transparency and a better return for their data from all those who collect it.