Ad servers are increasingly being used to display essential content for web sites (e.g., photos that are part of news items). Suppose that the same host is used to serve images for two different web sites. Explain why this is a threat to user privacy. Is this threat eliminated if the browser is configured to reject third-party cookies?

What will be an ideal response?

The owner of the image server can place a third-party cookie on the browser to
associate users with sessions on the two websites. Removing third-party cookies is effective
only if the server that provides images uses a host name outside of the domains of the two
websites. However, the same image server could be mapped to two different host names
in the domains of the two websites. Thus, session linking on different websites can be
accomplished even if third-party cookies are disabled.