The local press in Islington has just reported the accidental release of quite a bit of sensitive personal data by Islington council.

One of our volunteers, Helen, was responsible for spotting that Islington had made this mistake, and so we feel it is appropriate to set out a summary of what happened, to inform journalists and citizens who may be interested.

Note – Concerned residents should contact Islington Council or the Information Commissioner’s Office.

On 27th May a user of our WhatDoTheyKnow website raised an FOI request to Islington Borough Council. On the 26th June the council responded to the FOI request by sending three Excel workbooks. Unfortunately, these contained a considerable amount of accidentally released, private data about Islington residents. In one file the personal data was contained within a normal spreadsheet, in the two other workbooks the personal data was contained on four hidden sheets.

All requests and responses sent via WhatDoTheyKnow are automatically published online without any human intervention – this is the key feature that makes this site both valuable and popular. So these Excel workbooks went instantly onto the public web, where they seem to have attracted little attention – our logs suggest 7 downloads in total.

Shortly after sending out these files, someone within the the council tried to delete the first email using Microsoft Outlook’s ‘recall’ feature. As most readers are probably aware – normal emails sent across the internet cannot be remotely removed using the recall function, so this first mail, containing sensitive information in both plain sight and in (trivially) hidden forms remained online.

Unfortunately, this wasn’t the only mistake on the 26th June. A short while later, the council sent a ‘replacement’ FOI response that still contained a large amount of personal information, this time in the form of hidden Excel tabs. As you can see from this page on the Microsoft site , uncovering such tabs takes seconds, and only basic computer skills.

At no point on or after the 26th June did we receive any notification from Islington (or anyone else) that problematic information had been released not once, but twice, even though all mails sent via WhatDoTheyKnow make it clear that replies are published automatically online. Had we been told we would have been able to remove the information quickly.

It was only by sheer good fortune that our volunteer Helen happened to stumble across these documents some weeks later, and she handled the situation wonderfully, immediately hiding the data, asking Google to clear their cache, and alerting the rest of mySociety to the situation. This happened on the 14th July, a Saturday, and over the weekend mySociety staff, volunteers and trustees swung into action to formulate a plan.

The next working day, Monday 16th July, we alerted both Islington and the ICO about what had happened with an extremely detailed timeline.

The personal data released by Islington Borough Council relates to 2,376 individuals/families who have made applications for council housing or are council tenants, and includes everything from name to sexuality. It is for the ICO, not mySociety, to evaluate what sort of harm may have resulted from this release, but we felt it was important to be clear about the details of this incident.