Stanford University researchers found that Microsoft and several other high-profile companies were using a controversial technique to keep persistent cookies on users PCs to track their movements. Microsoft was using cookies that re-spawn even after users have deleted them. The company was using this technique on one of its sites, MSN.com, and now the company said that it is no longer doing so. In July, a graduate student at Stanford revealed that some companies were still employing techniques that enabled browser history sniffing, which give the companies information on what sites users have visited and what links they ve clicked on.
Source: https://threatpost.com/microsoft-drops-use-supercookies-msn-081911/75565/