Facebook trialling new technology to track users' behaviour online Site will record details like how long users hover their cursors over adverts Executive says data to be used for targeting ads and product development But increase in data collection will worry users concerned about privacy Facebook wants to get inside users heads with new capabilities to track and analyse their behaviour across the social network. Not content with collecting huge troves of data about users' lives outside of Facebook, executives want new capabilities to track users' minute interactions with the service itself. New technology would allow them to start collecting data on details like how long users hover their cursors over elements on the page and whether their newsfeed is visible as they browse the site. I just can't get you out of my head: Facebook is trialling new technology to allow it to precisely track users' interactions with the site, such as how long they hover their mouse cursors over adverts shown on the page Facebook analytics chief Ken Rudin said the recorded data could be used for various ends - ranging from product development to targeting advertising more precisely. But with the company among a string of Silicon Valley firms exploited for personal data by the U.S. National Security Agency, any increase in the data it collects is bound to raise users' concerns. It emerged last month that fears over privacy are prompting many to commit 'virtual identity suicide' by deleting their Facebook accounts. In a separate survey earlier this year more than half of those quitting Facebook cited privacy concerns as their main reason for doing so. It has long been said of online services like Facebook that users, who enjoy the site's features for free, are in fact the company's product rather than its customers. Data gold mine: Facebook collects two kinds of data about its users: demographic data, including where users' live or went to school; and behavioural data, such as users' online 'friends' and 'likes' Facebook is a rich mine of personal information about its more than a billion users, data it leverages commercially to target promotional campaigns precisely to advertisers' desired audiences. To this end, the company collects two kinds of data about its users: demographic data, including where users' live or went to school; and behavioural data, such as users' online 'friends' and 'likes'. Mr Rudin told the Wall Street Journal that the new technology, which is still in testing, would would massively expand the collection of that latter kind of data. Details recorded may include 'did your cursor hover over that ad ... and was the newsfeed in a viewable area,' said Mr Rudin, adding that he was not certain when the the capabilities would go live across Facebook. The social network would not be the first online service to make such a detailed record of users' interactions with its website. Digital image marketplace Shutterstock already records literally everything that its users do on the site, including where they place their cursosrs and how long they hover over a picture before buying it. Shutterstock uses open-source software called Hadoop to analyse the data, the same technology Facebook already uses a modified form of to manage its data. The Journal reported that Facebook has expanded the hardware in its data analytics warehouse a staggering 4,000 times in four years to a current capacity of 300 petabytes. That's equivalent to 300million gigabytes, which is 600,000 times the capacity of a typical 500GB laptop hardrive or equal to the storage space on around 470,000 top-of-the-range 64GB iPhones. That massive amount of data is distinct from the demographic data stored by Facebook, which has never disclosed how much of the latter it holds.