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Can I delete cookies?
How do I set my browser to reject cookies?
Are cookies dangerous to my computer?
Will cookies fill up my hard drive?
Are cookies a threat to my privacy?
Sites are telling me I need to turn on
cookies, but they are on. What's wrong?
I deleted my cookies, and I can't log-on to
my favorite site anymore. What can I do?
How did I get a cookie from
doubleclick?
I've never been there!
I looked at my Internet Explorer cookies,
and they had my username on them! Can servers see my
username?
There are two extra files in my Cookies
folder called Mm256.dat and Mm2048.dat. What are they?
Can I delete cookies?
Yes. Whether you use Internet Explorer or Netscape, your cookies are
saved to a simple text file that you can delete as you please.
In order to do this properly, remember to close your browser first.
This is because all your cookies are held in memory until you close your
browser. So, if you delete the file with your browser open, it will make
a new file when you close it, and your cookies will be back.
Remember that deleting your cookie file entirely will cause you to
"start from scratch" with every web site you usually visit.
So, it may be preferable to open the cookies.txt file (in the case of
Netscape) and remove only the entries you don't like, or go to the
cookies folder (in the case of IE) and delete the files matching servers
you don't want.
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How do I set my browser to
reject cookies?
Both Internet Explorer and Netscape allow some level of cookie
verification. They both have menu options that allow you to accept all,
some, or none of your incoming cookies. In addition, the "warn
before accepting" feature is present in both, if you want to screen
your incoming cookies.
In Netscape, go to the Edit/Preferences/Advanced menu. Your
cookie choices can be changed there.
Microsoft has changed their approach to cookies over the last 3 versions
of their browser. This is a reflection of how cookies have been thrust
into the limelight of privacy on the Internet:
- In IE 6.0, go to the Tools/Internet Options/Privacy
menu. This menu allows you to select how discriminating the browser
will be when accepting cookies, based on two factors -- (1) the
source of the cookie, and (2) whether the source has a "privacy
policy." There are also features for the advanced user, if
you'd like to have a greater control over cookies. [more
info]
- In IE 5.0, go to the Tools/Internet Options/Security
menu. In there, you can choose the security level for 4 different
browsing conditions: Internet Sites, Local Sites,
"Trusted" Sites, and Restricted Sites. If you select
"Internet," and click on Custom Level, you'll get a dialog
box where you can accept all, warn before accepting, or reject all
cookies. [more
info]
- In IE 4.0, go to the View/Internet Options/Advanced
menu. There you can accept all, warn before accepting, or reject
all.
Once a cookie is rejected, it is thrown out and not saved to memory or
disk. Don't forget, though, that servers will keep looking for the
cookie even if you have discarded it and may try to replace it as you
surf around.
This fact is almost comical in nature. Essentially, by removing the way
to tell the server to not send cookies, it can't remember to not send
you any cookies the next time!
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Are Cookies Dangerous to My
Computer?
NO. A cookie is a simple piece of text. It is not a program, or a
plug-in. It cannot be used as a virus, and it cannot access your hard
drive. Your browser (not a programmer) can save cookie values to your
hard disk if it needs to, but that is the limit of the effect on your
system.
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Will cookies fill up my hard
drive?
Both Netscape and Microsoft have measures in place that limit the number
of cookies that will be saved on your hard drive at one time.
Both Internet Explorer and Netscape conform to the RFC 2109 limitations
on your total cookie count to 300 (this includes a limit of 20 cookies
per individual domain). If you exceed this, the browser will discard
your least-used cookies to make room for the new ones.
Microsoft saves cookies into the "Temporary Internet Files"
folder, a system folder that you can set the maximum size of (the
default is 2% of your hard drive).
In any event, remember that most cookie files are 4KB or smaller, so you
would need about a million cookies to fill up a 4GB drive. This is
incredibly unlikely.
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Are Cookies a Threat to My
Privacy?
The sad truth is that revealing any kind of personal information opens
the door for that information to be spread.
Consider the growing trend of technology conveniences in our lives. We
use "frequent buyer" cards at supermarkets and gas stations.
We place electronic tags on our cars to pay tolls faster and easier. We
let banks pay our bills for us automatically each month without checks.
While each of these technologies (and others like them) have made our
lives more convenient, each time we use them exposes us to a loss of
privacy. Stores know what foods you eat. Gas stations know how much you
spend on gas per fill-up. Turnpike operators know how fast you drive on
their highways. Banks know how you spend your money each month.
It's the same with cookies. In fact, one may argue that cookies in the
long-run will be less damaging to privacy efforts than those
technologies described above. If you're going to single-out cookies as
your sole vulnerability to personal privacy, you should re-examine how
you live your daily life.
The never-ending ethical debate associated with these facts shall be
left to other forums. However, it is wise to consider carefully the
information you collect and share over the Internet.
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Sites are telling me I need to
turn on cookies, but they are on. What's wrong?
There are three likely possibilities for problems like this. Firstly,
the site you are visiting may be detecting cookies improperly. As a
result, it may appear to the site that you are rejecting cookies when in
fact you are not.
Another possibility is that you may be running software that interferes
with cookie usage. There are many filtering and blocking software
packages available for Internet users these days, and many of them also
filter cookies. If you are running software like this, then your
computer may not receive or send cookies. This will cause sites you
visit to assume you are not accepting cookies.
Finally, your machine may be behind a firewall or proxy server that
prevents cookie transmission. This is most likely in a corporate
environment. So, regardless of how your browser is set, cookies won't be
sent or received by your browser. Since the cookies aren't making it
through to your browser, the Web Site will assume you personally aren't
accepting them.
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I deleted my cookies, and I
can't log-on to my favorite site anymore. What can I do?
Many sites use a cookie to keep track of your settings on their servers,
and to help you log in to their site. If you lose your cookie, that site
cannot recall your settings for you to use.
If this happens to you, the best thing you can do is contact that site's
webmaster or customer service department.
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How did I get a cookie from
doubleclick? I've never been there!
In section 3.3, we'll see that a server cannot set a
cookie for a domain that it isn't a member of. However, almost every Web
user has gotten a cookie from "ad.doubleclick.net" at one time
or another, without ever visiting there. DoubleClick and other
advertisers have employed a clever solution that enables them to track
users and serve media content without violating this rule.
Most sites on the Internet do not keep their advertisements locally.
Rather, they subscribe to a media service that places those ads for
them. This is accomplished via a simple HTML call to the media service.
When a page is requested, it is assembled through many HTTP requests by
the browser. First, there is a request for the HTML itself. Then,
everything the HTML needs is requested, including images, sounds, and
plug-ins.
The call to the media service is an HTTP request for an image. Once the
request is made to the media service, it can return more than just an
ad. It can also return a cookie. Or, if is has given the user a cookie
previously, it can read that first, and check to see what ad to send.
The net result is that the user gets a cookie from the media service
without ever having visited it.
This usage of cookies is the most controversial, and has led to the
polarized opinions on cookies, privacy, and the Internet.
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I looked at my Internet
Explorer cookies, and they had my username on them! Can servers
see my username?
Because Windows systems allow more than one user to login and use
programs, Microsoft had to come up with a way to keep each user's
cookies separate on a given machine. This can be common in workplaces,
where a single machine is shared by many employees.
This is accomplished by appending the username to the cookie file name.
This way, both Jane Doe and Joe Smith can get cookies from coolsite.com
and they don't get over-written. Also, this stop's Jane from using Joe's
cookies while she's surfing, since the browser will only use her cookies
when she is logged in. That is, the cookie file:
jdoe@coolsite.txt
Contains
Jane Doe's cookie for coolsite.com. If anyone else logs-in, then this
cookie is not used.
This is the only reason that the username is part of the cookie file
name. The username does not get sent to the server with the
cookie data.
There are two extra files in
my Cookies folder called Mm256.dat and Mm2048.dat. What are they?
You can read more about this on Microsoft's Knowledge
Base.
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Copyright ©1997-2002
David Whalen. This document is provided "as is" without any
guarantees or warranty. Although the author has attempted to find and
correct any errors or mistakes he, and everyone who contributed to it,
are not responsible for any damage or losses of any kind caused by the
use or misuse of information in this FAQ. The author is under no
obligation to provide service, corrections, or upgrades to this FAQ.
The following is legal information and refers to all the information in
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