The controversy over the 2o7.net cookies highlights the tension that exists between marketing companies like Omniture and Web users who are increasingly aware of, and adverse to, files that are automatically placed on their computers when they surf the Internet. At a time when PCs are under assault by viruses and other nefarious software like never before, users are employing a range of software tools and tactics to protect themselves. Many users don’t distinguish between cookies, which are small bits of text commonly used by Web sites to identify users, and malicious software that can steal personal information or change PC settings. That has put marketers on the defensive, as they try to get users to spare cookies when wiping computers clean of potential threats.