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Cyber Security Tip ST05-008
How Anonymous Are You?
You may think that you are anonymous as you browse web sites, but
pieces of information about you are always left behind. You can reduce
the amount of information revealed about you by visiting legitimate
sites, checking privacy policies, and minimizing the amount of
personal information you provide.
What information is collected?
When you visit a web site, a certain amount of information is
automatically sent to the site. This information may include the
following:
* IP address - Each computer on the internet is assigned a specific,
unique IP (internet protocol) address. Your computer may have a
static IP address or a dynamic IP address. If you have a static IP
address, it never changes. However, some ISPs own a block of
addresses and assign an open one each time you connect to the
internet--this is a dynamic IP address. You can determine your
computer's IP address at any given time by visiting
www.showmyip.com
* domain name - The internet is divided into domains, and every
user's account is associated with one of those domains. You can
identify the domain by looking at the end of URL; for example,
.edu indicates an educational institution, .gov indicates a US
government agency, .org refers to organization, .com is for
commercial use. Many countries also have specific domain names.
The list of active domain names is available at
http://www.iana.org/domain-names.htm or
http://www.norid.no/domenenavnbaser/domreg.html.
* software details - It may be possible for an organization to
determine which browser, including the version, that you used to
access its site. The organization may also be able to determine
what operating system your computer is running.
* page visits - Information about which pages you visited, how long
you stayed on a given page, and whether you came to the site from
a search engine is often available to the organization operating
the web site.
If a web site uses cookies, the organization may be able to collect
even more information, such as your browsing patterns, which include
other sites you've visited. If the site you're vising is malicious,
files on your computer, as well as passwords stored in the temporary
memory, may be at risk.
How is this information used?
Generally, organizations use the information that is gathered
automatically for legitimate purposes, such as generating statistics
about their sites. By analyzing the statistics, the organizations can
better understand the popularity of the site and which areas of
content are being accessed the most. They may be able to use this
information to modify the site to better support the behavior of the
people visiting it.
Another way to apply information gathered about users is marketing. If
the site uses cookies to determine other sites or pages you have
visited, it may use this information to advertise certain products.
The products may be on the same site or may be offered by partner
sites.
However, some sites may collect your information for malicious
purposes. If attackers are able to access files, passwords, or
personal information on your computer, they may be able to use this
data to their advantage. The attackers may be able to steal your
identity, using and abusing your personal information for financial
gain. A common practice is for attackers to use this type of
information once or twice, then sell or trade it to other people. The
attackers profit from the sale or trade, and increasing the number of
transactions makes it more difficult to trace any activity back to
them. The attackers may also alter the security settings on your
computer so that they can access and use your computer for other
malicious activity.
Are you exposing any other personal information?
While using cookies may be one method for gathering information, the
easiest way for attackers to get access to personal information is to
ask for it. By representing a malicious site as a legitimate one,
attackers may be able to convince you to give them your address,
credit card information, social security number, or other personal
data (see Avoiding Social Engineering and Phishing Attacks for more
information).
How can you limit the amount of information collected about you?
* Be careful supplying personal information - Unless you trust a
site, don't give your address, password, or credit card
information. Look for indications that the site uses SSL to
encrypt your information (see Protecting Your Privacy for more
information). Although some sites require you to supply your
social security number (e.g., sites associated with financial
transactions such as loans or credit cards), be especially wary of
providing this information online.
* Limit cookies - If an attacker can access your computer, he or she
may be able to find personal data stored in cookies. You may not
realize the extent of the information stored on your computer
until it is too late. However, you can limit the use of cookies
(see Browsing Safely: Understanding Active Content and Cookies for
more information).
* Browse safely - Be careful which web sites you visit; if it seems
suspicious, leave the site. Also make sure to take precautions by
increasing your security settings (see Evaluating Your Web
Browser's Security Settings for more information), keeping your
virus definitions up to date (see Understanding Anti-Virus
Software for more information), and scanning your computer for
spyware (see Recognizing and Avoiding Spyware for more
information).
_________________________________________________________________
Author: Mindi McDowell
_________________________________________________________________
This document can also be found at
<http://www.us-cert.gov/cas/tips/ST05-008.html>
Copyright 2005 Carnegie Mellon University
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