Monday, June 21, 2010

How Anonymous Are You?

Cyber Security Tip ST05-008
How Anonymous Are You?

You may think that you are anonymous as you browse websites, 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

What information is collected?

When you visit a website, 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
* 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, and .com is for commercial use. Many countries
also have specific domain names. The list of active domain names is
available from the Internet Assigned Numbers Authority (IANA).
* 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 website.

If a website 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 visiting is malicious, files on your
computer, as well as passwords stored in the temporary memory, may be at

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

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 websites 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).

Additional information

* Securing Your Web Browser

Author: Mindi McDowell

Produced 2005 by US-CERT, a government organization.

Note: This tip was previously published and is being
re-distributed to increase awareness.

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