This is a problem we have been warning about for some time. Islington Council were fined £70,000 for a similar incident in 2012. In light of this fresh incident we again urge all public authorities to take care when preparing data for release.
As with the Islington incident, the information was in parts of an Excel spreadsheet that were not immediately visible. It was automatically published on 14th November when Hackney Council sent it in response to a Freedom of Information request, as part of the normal operation of the WhatDoTheyKnow website. All requests sent via the website make it clear that this will happen.
This particular breach involved a new kind of hidden information we hadn’t seen before – the released spreadsheet had previously been linked to another spreadsheet containing the private information, and the private information had been cached in the “Named Range” data in the released spreadsheet.
Although it was not straightforward to access the information directly using Excel, it was directly visible using other Windows programs such as Notepad. It had also been indexed by Google and some of it was displayed in their search previews.
The breach was first hit upon by one of the data subjects searching for their own name. When they contacted us on 25th November to ask about this, one of our volunteers, Richard, realised what had happened. He immediately hid the information from public view and notified the council.
We did not receive any substantive response from the council and therefore contacted them again on 3rd December. The council had investigated the original report but not understood the problem, and were in fact preparing to send a new copy of the information to the WhatDoTheyKnow site, which would have caused the breach to be repeated.
We reiterated what we had found and advised them to consult with IT experts within their organisation. The next day, 4th December, we sent them a further notification of what had happened, copying the Information Commissioner’s Office (ICO). As far as we are aware, this was the first time the ICO was informed of the breach.
From our point of view it is very disappointing that these incidents are still happening. Freedom of Information requests made via WhatDoTheyKnow are a small fraction of all requests, so it is very likely that this kind of error happens many more times in private responses to requesters, without the public authority ever becoming aware.
Our earlier blog post has several tips for avoiding this problem. These tips include using CSV format to release spreadsheets, and checking that file sizes are consistent with the intended release. Either of these approaches would have averted this particular breach.
We would also urge the ICO to do as much as possible to educate authorities about this issue.