CookieCutter is a little program I wrote that allows you to display, modify, and even delete cookies. Since the banner-ad-tracking firm DoubleClick probably keeps a lot of information on your browsing habits, you want to befuddle them. After all, they are using a tiny bit of storage on your hard disk to rack up per-click profits, giving you nothing in return (directly, at least; obviously, ad sponsorship keeps some web sites on the air). In Figure 18-10, I am editing the cookie to, umm, “update” the personal identity cookie to an invalid number (a lot of 9’s, and too many digits). A few lines above that, you can see the prefs.bgcolor cookie that I set to “green.”

Figure 18-10. The CookieCutter display

I won’t show the CookieCutter source code here as it doesn’t really relate to web techniques (it’s a client-side application), but it’s included in the source archive for the book. CookieCutter also assumes your cookies are stored in the Netscape format; for the Microsoft Explorer format, you’ll have to change the file-reading and file-writing code.