This post was written by Cynthia O’Donoghue.

The Information Commissioner’s Office (“ICO”) has asked Google to explain the operation of its system of delivering ‘third-party’ cookies to Internet users, spurred on by a dispute that has arisen between Google and Microsoft regarding Internet Explorer privacy policies.
The dispute arose when Dean Hachamovitch, Corporate Vice President for Internet Explorer (“IE”), wrote a blog post in which Microsoft accused Google of using ‘third-party’ cookies to track user behaviour online, when IE has default settings in place to stop this from occurring. ‘Third-party’ cookies are those dropped by domains other than the current domain in the address bar. They are valuable to advertisers as they can assist in building a browsing history of a user across all of the websites he or she visits.

IE by default blocks ‘third-party’ cookies unless a site presents a ‘Platform for Privacy Preferences’ (“P3P”) Compact Policy Statement describing how the site will use the cookie and pledging not to track the user. Microsoft claims Google’s P3P policy causes IE to accept Google’s cookies even though it does not say how it will use them, by utilising a nuance in the P3P specification. By using specific text, browsers read Google’s policy as saying that the cookie won’t be used for tracking or any similar purpose, enabling Google to bypass the cookie protection and permitting the use of ‘third-party’ cookies rather than blocking them.

Rachel Whetstone, Senior Vice President of Communications and Policy at Google, said Microsoft had "omitted important information" from the blog post. She insisted that it was well known that Microsoft’s system is outdated (dating back to 2002), and that it is “impractical to comply with Microsoft’s request while providing modern web functionality”.

An ICO spokesperson has confirmed that it is making “ongoing enquiries” with Google over Microsoft’s claims in order to ensure that Google is complying with both the Data Protection Act and EU privacy regulations. The ICO could not comment on when these enquiries would be completed.

Microsoft’s blog post follows an article published 17 February 2012 in the Wall Street Journal, which accused Google of using a special coding to circumvent privacy policies in Apple browser Safari, allowing it to track user movement across websites.