Getting Stuffed With Cookies When You Browse?
By Rich Luhr. Published in Internet Medicine, March, 1997
Although its easy to get the impression when browsing the web that one is doing so anonymously, your activities might be tracked in several ways. One of the most popular techniques for tracking usage is the "cookie", and even if youve heard of them before, you might be surprised at what they can do.
A cookie is like a passport in your computer. Whenever you visit a web site, the web server can send a cookie to your computer, which is then stored on your hard drive. As you visit additional sites, you may pick up additional cookies. Each cookie can be a miniature record of your visit to a specific web site, complete with information such as an ID number, time of your last visit to that specific site, and any other information that you give up willingly such as password or email address.
The effect is something akin to "Caller ID" on telephones. By retrieving the cookie left previously, a web site can "remember" your site-specific password, your preferences, and other tidbits of information. When you re-visit a site, a cookie left on your hard drive will identify you.
In other cases, cookies are being used to keep track of how many visitors visit a site. These types of cookies dont get stored permanently in your computer they expire immediately, so they cant be used to determine how often you re-visit the site.
Advocates of cookies point out that cookies can streamline and improve your use of web sites. For example, when visiting The New York Times Online (www.nytimes.com), you will only have to enter your password once. The next time you visit, a cookie will tell the web server who you are and youll be able to bypass the usual password-protected sign-on screen.
On the other hand, The New York Times could easily track how often you visit their site, what sections of the paper you read, and even estimate how long you spent there.
Naturally, discovering the existence of such a tracking mechanism has created some alarm among web users. Although cookies arent intrinsically malevolent, many have foreseen that cookies could be used to develop a profile of individuals which could then be used for marketing, or perhaps more nefarious, purposes. Privacy advocates consider this to be potentially an invasive act.
Well tell you how to disable cookies in your web browser later in this article, but first, some Q&A about cookies will help you understand what they can and cannot do.
Q: When is a cookie really useful to me?
Q: What cant cookies do?
A: Cookies cannot enable the web server to read from your hard drive, get your e-mail address against your will, destroy files on your computer, or create executable programs. Cookies can only contain as much information about you as you disclose on the site which sets the cookie.
Q: If a cookie is stored on my hard drive, wont that consume a lot of disk space eventually?
A: Not really. Cookies are limited to 4k in size, and most are much smaller, so you would have to visit thousands of web sites using cookies to consume even a single megabyte of disk space.
Q: Who can see my cookies?
A: A cookie is specific to a web server. Only the web server that set the cookie initially can retrieve it later. So, no one can retrieve all of your cookies to develop a profile of your web browsing habits.
Q: Since theyre downloading something to my hard drive, should I be concerned about viruses?
A: No, cookies are limited to text-only, and cant be executed. Therefore, its impossible that a cookie could contain a virus.
A: No, but
surprisingly, any web site can get information regarding what
operating system and browser software you are using (for example,
Win95/Netscape), and the address of the last site you visited
without using cookies!
(For a demonstration, visit www.anonymizer.com/cgi-bin/snoop.pl)
Q: Do they ever go away?
A: All cookies have expiration dates (like the store-bought kind), but usually those expiration dates are either years in the future, or immediately after the web session ends, depending on what the cookie is being used for.
Q: Are cookies a security risk?
A: They could be, in a small way. If your computer is networked to others, there is a possibility that someone could access your cookie file and read it. If some of your cookies contained passwords that you use for particular web sites, that information would be readily available. To combat this, most web sites dont set cookies with anything more than an encrypted ID number. You should also make a habit of using different passwords for web sites than you do for more critical things, like locking your computer or your ATM card.
If you want to get examine what cookies youve already accumulated, look for a file called COOKIES.TXT on your hard drive. In Windows95 PCs you can use Windows Explorer, Tools, Find, Files or Folders... option to locate the file.
Killing The Cookie Monster
If youve decided you dont want to be tracked with cookies, you have several options:
First, you can tell Netscape Navigator to alert you whenever a web site is trying to set a cookie on your computer. In Netscape, select Options Network Preferences. From the window that appears, select the Protocols tab. Locate the section Show An Alert Before, and check the box marked Accepting a Cookie. Theres a similar procedure for Microsoft Internet Explorer: Go to the Control Panel (from the Start button), and click on the Internet icon, then select the Advanced tab. Check the box marked Warn before accepting cookies.
If you follow this procedure, youll get a warning every time a cookie is sent and be able to choose whether to allow it or not. If you select "Cancel", the cookie wont be set. In most cases, the web site acts normally, but in some cases this can cause the web site to display incorrectly. The disadvantage of this method is that some sites attempt to send a cookie with every image, meaning that you can be clicking "Cancel" a lot before the web site finally appears.
Neither Internet Explorer nor Navigator allow you to turn off cookies completely, so your second option to kill the cookie monster is a little more extreme: You can periodically locate and delete the file COOKIES.TXT. This will, of course, wipe out all cookies stored on your computer. Theoretically, you could also edit out only the cookies you dont want, using a text editor. Think of this as "tossing your cookies".
Incidentally, PGP, a privacy-software firm (www.pgp.com) intends to offer a "cookie blocking" program for PC users soon. These are the same people who created the famous "Pretty Good Privacy" encryption software.
Your third option is the most radical. Write-protect the COOKIES.TXT file. In Internet Explorer, you will get a message every time a cookie is set, to the effect that your cookie file is missing or corrupted, which is annoying. Netscape, however, blithely ignores the problem and the cookies simply arent stored. You can write-protect the file using Windows Explorer: right-click on COOKIES.TXT, select "Properties", and on the window that pops up, check the box marked "Read only". Note that this approach isnt sanctioned by Netscape or Microsoft.
Overall, cookies are like most other bits of technology: useful if used properly, but dangerous if mismanaged. If you dislike others tracking your use of their website, then you have options to protect yourself. If you are ambivalent about being tracked, then cookies can be very useful, and best of all, they are completely automatic.