Transcript Department of Information Technology

Department of Information Technology
Chapter 12: securing &
Enhancing Internet usage
Prepared by: Ms Melinda Chung
Objectives
Department of
Information Technology

Investigate the different kinds of computer threats.

Identify countermeasures for protecting yourself and your
computer while using the Internet.

Learn how to protect copyrighted materials that are
published on the Internet.
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Objectives
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
Learn how to enhance your Web browser with
browser extensions.

Use popular plug-ins to view animated Web site
content.
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Locate and use browser extensions.
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Security Overview
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Information Technology

Security - the protection of assets from unauthorized
access, use, alteration, or destruction.

Physical security - includes tangible protection devices
(e.g. locks, alarms, fireproof doors, security fences, safes
or vaults, and bombproof buildings).

Logical security - Protection of assets using non-physical
means.
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Security Overview
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
Any act or object that endangers an asset is known as a
threat.

Countermeasure is the general name for a procedure, either
physical or logical, that recognizes, reduces, or eliminates a
threat.

Countermeasures can recognize and manage threats or they
can eliminate them.
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Risk Management Model
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High Probability
Low
Impact
(cost)
Contain and
control
Ignore
Prevent
Insurance or
backup plan
High
Impact
(cost)
Low Probability
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Security Overview
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Information Technology

To implement a good security scheme, need to identify the
risk, determine how to protect the affected asset, and calculate
the cost of the resources you can allocate to protect the asset.

Computer security can be classified into several categories:
 Secrecy


Integrity
Necessity
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Security Overview
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
Secrecy prevents unauthorized data disclosure and ensures the
authenticity of the data’s source (Confidentiality)

Integrity prevents unauthorized data modification.

Necessity prevents data delays (slowing down the transmission of
data) or denials (preventing data from getting to its destinations
(Availabiity)

Need appropriate countermeasures for these 3 categories to
protect themselves (users, businesses) and the computers used to
connect to the Internet.
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Encryption
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
Encryption - the process of coding information using a
mathematical-based program and a secret key to produce
a string of characters that is unreadable.

Decryption - the process of reversing encrypted text. In
order to decrypt text, you need a key to “unlock” it.

Encrypted information is called cipher text.

Unencrypted information is called plain text.

The process of transforming data from a readable format
(plain text) to an unreadable format (cipher text) is called
cryptography.
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Encryption
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Private-key encryption (symmetric encryption)
uses a single key that is known by the sender and
receiver.

The key might be a password or a number
generated by a special device.

Private-key encryption works well in a highly
controlled environment.
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Private-key (Symmetric)
Encryption
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common
key
encrypt
decrypt
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Encryption
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
Public-key encryption (asymmetric encryption) uses
two different keys—a public key and a private or secret
key.

The public key is known to everyone.

The private or secret key is known only to the person who
owns both keys.

With public-key encryption, each person has a private
key that is secret and a public key that is shared with
other users.

Messages encrypted with a private key must be decrypted
with the public key, and vice versa.
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Public-key (asymmetric)
Encryption
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encrypt
decrypt
public key
private key
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Encryption
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
Encryption is considered to be weak or strong based
on its algorithm and the number of characters in the
encryption key.

A cracker is a person who uses his knowledge of
computers and programming to gain unauthorized
access to a computer for the purpose of stealing or
altering data.

Keys that are 128 bits long are called strong keys.
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Using Certificates for
Authentication and Identification
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Information Technology

Phishing is an attack involving phony e-mail messages
that include links to Web sites that “fish” for sensitive
information (password, credit card numbers).
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Authentication is the process of correctly verifying the
identify of a person or a Web site.

The primary countermeasure for authentication is a
digital certificate.
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A digital certificate is an encrypted and passwordprotected file that contains sufficient information to
authenticate and prove a person’s or organization’s identity.
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Using Certificates for
Authentication and Identification
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
A digital certificate is an electronic equivalent of an
identification card.

A certificate authority (CA) is a trusted third party
which verifies the certificate holder’s identity and
issues the digital certificate.
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A digital ID (personal certificate) is used to identify a
person to other people and to Web sites that are set
up to accept digital certificates.

A digital ID is an electronic file that you purchase from
a certificate authority and install into a program that
uses it, such as a Web browser.
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Using Certificates for
Authentication and Identification
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The digital ID authenticates the user and protects data
transfer online from being altered or stolen.
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A server certificate (SSL Web server certificate)
authenticates a Web site for its users so the user can be
confident that the Web site is genuine and not an imposter.

A server certificate also ensures that the transfer of data
between a user’s computer and the server so that it is both
tamperproof and free from being intercepted.
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Processing a Certificate
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client 1
server
client 2
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Using Certificates for
Authentication and Identification
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User identification - the process of identifying yourself to a
computer.
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Most computer systems implement user identification with
user names and passwords; login - the combination of a
user name and password.

To help keep track of their login information for different
computers and Web sites, use a program called a
password manager, which stores login information in an
encrypted form on their computer.
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Using Certificates for
Authentication and Identification
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Crackers can run programs that create and enter
passwords from a dictionary or a list of commonly
used passwords.
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A brute force attack occurs when a cracker uses a
program to enter character combinations until the
system accepts a user name and password, thereby
gaining access to the system.
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User authentication is the process of associating a
person and his identification with a very high level of
assurance.
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Secure Sockets Layer (SSL)
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Secure Sockets Layer (SSL) is a widely used protocol that
acts as a separate layer or “secure channel” on top of the
TCP/IP Internet protocol.
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SSL provides a security handshake when a browser and
the Web page to which it is connected want to participate in
a secure connection.
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Web pages secured by SSL have URLs that begin with
https:// instead of http://.
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Secure State Indicator
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Internet Explorer
Navigator
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Secure Sockets Layer (SSL)
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SSL creates a public-key pair so that it can safely transmit
data using a private key.
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The private key is encrypted using public-key encryption
and is sent to the browser. Using the private key protects
the remainder of the information transfer between the
browser and the Web site.
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When the user leaves the secure Web site, the browser
discards these temporary keys, or session keys.

Session keys exist only during a single, active session
between a browser and server.
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Managing Cookies
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A cookie is a small text file that a Web server
creates and stores on your computer’s hard drive.
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A cookie stores data of the links you click while
visiting the Web site (called a clickstream),
information about the products you purchase, or
personal information provided to the site.
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Some cookies are removed automatically when
you leave a Web site (a session-only cookie).
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Managing Cookies
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Web sites use cookies to make it easier to navigate sites.
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A cookie is not a program and it can only store information
that you provide to the Web site that creates it.
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Sometimes cookie gets the data openly, other times, it
might silently record your behavior at a Web site.
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Only the Web site that stored the cookie on your hard drive
can read it, and it cannot read other cookies on your hard
drive or any other file on your computer.
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Managing Cookies
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Cookies can cause a security threat for some users.
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Internet users can control the storage of cookies on their
computer’s hard drive by changing their browser’s settings.
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The best way to prevent another user from gaining access
to information is to make sure that you do not leave an
electronic trail to its path.
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Internet Explorer stores cookies in C:\Windows\Cookies folder.
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Navigator stores cookies in a file named cookies.txt on the user’s hard
drive.
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Managing Cookies in
Internet Explorer
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Managing Cookies
in Navigator
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Web Bugs, Spyware,
and Adware
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
A Web bug is a small, hidden graphic on a Web page or in
an e-mail message that is designed to work in conjunction
with a cookie to obtain information about the person
viewing the page or e-mail message and to send the
information to a third party.

When the user loads the Web page that contains this code,
the browser downloads the hidden graphic. This process
can identify your IP address, the Web site you last visited,
and other information about your use of the site in which
the clear GIF file has been embedded and record it in the
cookie file.
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HTML for a Web Bug
Clear GIF
file
location
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<FRAMESET ROWS=“*.20” BORDER=0 FRAMEBORDER=0
FRAMESPACING=0>
<!– Start of Doubleclick Tracking Code: Please do not remove -->
<script LANGUAGE=“javascript”>
var axel = Math.random( )+” “;
document.write(‘ <IMG
SRC=http://ad.doubleclick.net/activity;src=585966;type=counter;cat=oran;or
d=1;num=‘ + a + ‘?
WIDTH=1 HEIGHT=1 BORDER=0>’);
</SCRIPT>
Cookie identification
number generated for the
<noscript>
current user
<img src=‘http://127.0.0.1:3388/bug.cgi’>
</NOSCRIPT>
<!– End of Doubleclick Tracking Code: Please do not remove -->
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Web Bugs, Spyware,
and Adware
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Information Technology

Adware is a general category of software that includes
advertisements to help pay for the product in which
they appear.

In many freeware and shareware programs, adware
provides opportunities for developers to offer software
at little or no cost to the user.

Adware usually does not cause any security threats
because the user is aware of the ads and the parties
responsible for including them are clearly identified in
the programs.
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Web Bugs, Spyware,
and Adware
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Information Technology

Spyware is a category of adware in which the user
has little control over or knowledge of the ads and
other monitoring features it contains.

Spyware occurs in situations where a developer has
sold ads to a third party or embedded other features in
the program.
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A Web bug is an example of spyware because the
clear GIF and its actions are hidden from the user.
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Web Bugs, Spyware,
and Adware
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Information Technology

One way to protect computers from the potential
privacy violations created by cookies, Web bugs, and
spyware is to set Web browsers to block third-party
cookie files.
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There are many good shareware programs that erase
spyware from your computer.
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These programs, sometimes called ad blockers,
search for files written by known spyware.
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Firewalls
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A firewall is a software program or hardware device that
controls access between two networks, such as a local
area network and the Internet or the Internet and a
computer.

A port on a computer is like a door; it permits traffic to
leave and enter a computer. When the port is closed, traffic
can’t leave or enter the computer.

A port scan occurs when one computer tests all or some of
the ports of another computer to determine whether its
ports are open, closed, or stealth.
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Basic Firewall Architecture
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Firewalls
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
Some firewall software programs are available for
free or at a very low cost so they are become
popular with other types of users.

Some antivirus programs and Internet suites
include basic firewall protection.
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Integrity Threats and
Countermeasures
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
An integrity threat occurs when an unauthorized party has
the chance to alter data while it is being transferred over
the Internet or while it is stored on a computer.

The most visible integrity threats - Trojan horses, viruses,
and worms that attack computers and the programs they
run.

A Trojan horse is a small program hidden inside another
program that causes harm when the user accesses or
downloads the program in which it is hidden.
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Integrity Threats and
Countermeasures
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A worm, a type of virus, self-replicating program that is hidden
within another file and then sent as an e-mail attachment.
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A worm can replicate itself on a computer or server, but it
cannot infect other files.
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The best defense against a worm:
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install an antivirus program;
update your virus patterns regularly;
display Windows filename extensions so you can determine the
type of file you have downloaded;
avoid opening attachments that you are not expecting.
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Protecting E-Mail Messages
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To maintain the integrity of an e-mail message - send the
message through a message digest function program
(hash code function program) to produce a number
called a message authentication code (MAC).
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After it receives the MAC, the e-mail program sends the
message and matching MAC together to the recipient.

The recipient’s e-mail program recomputes the message’s
MAC & compares the computed MAC to the received MAC.
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If they match, the content of the message is unaltered. If
they do not match, then the message cannot be trusted.
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Producing a MAC for
a Message
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Protecting E-Mail Messages

To be useful, the message digest function must exhibit
the following characteristics:

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
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It is impossible or costly to reverse the MAC and
produce the original message.
The MAC should be random.
The MAC must be unique to the message.
You can also protect outgoing e-mail messages with
the Secure/Multipurpose Internet Mail Extensions
(S/MIME) specification, which when combined with a
person’s digital ID provides authentication and
encryption to e-mail messages.
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Necessity Threats and
Countermeasure
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Necessity occurs when a cracker uses a program to
disrupt normal computer processing or, possibly, to deny
processing entirely.
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A packet flooding attack or denial of service (DoS)
attack occurs when a cracker bombards a server or other
computer with messages in an attempt to consume the
network’s bandwidth resources.

Delaying processing can render a service unusable or
unattractive.
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Necessity Threats and
Countermeasure
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One of the most dangerous entry points for delay and denial
threats come from coded programs that travel with applications
to a browser and execute on the user’s computer.

A Java applet (a program written in the Java programming
language), could execute and consume a computer’s resources.

A JavaScript program can pose a problem because its
programs can run without being compiled before running on a
computer.

ActiveX components are Microsoft’s technology for writing
small applications that perform some action in Web pages—
these components have full access to a computer’s file system.
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Copyright & IP Threats and
Countermeasures
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
Copyright and safeguarding IP (intellectual property)
rights are also security issues.

IP threats are a large problem due to the Internet and
the relative ease with which one can use existing
material without the owner’s permission.
 It is very simple to reproduce an exact copy of
anything you find on the Internet.
 Many people are naïve or unaware of copyright
restrictions that protect intellectual property.
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Copyright & IP Threats and
Countermeasures
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A digital watermark is a process that inserts a
digital pattern containing copyright information into
a digital image, animation, or audio or video file.

Steganography is a process that hides an
encrypted message within different types of files.
It can be used to add copyright information to
different types of files.
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Enhancing the Use of Internet
with Browser Extensions
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Browser extensions & plug-ins:
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Browser extensions: allow a browser to perform more tasks.

Plug-in: integrated browser software that the browser uses to
display/play a specific file upon request.

Plug-ins do their work inside the browser. Many plug-ins are
installed together with the browser.

main difference: plug-ins rely on the main application's user
interface and have a well-defined boundary to their possible set
of actions. Extensions have fewer restrictions on their actions,
and may provide their own user interfaces.
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Enhancing the Use of Internet
with Browser Extensions
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Helper applications & add-ons:

Helper applications: are independent programs that are
stored on user’s computer and are activated automatically
when needed.

Helper applications: used by the browser to start and to
“help” display or play a file.

Add-ons: include tools that enhance your browsing
experience, such as toolbars or programs that block pop-up
ads from opening.
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Enhancing the use of Internet
with Browser Extensions

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Browser extensions are often grouped into categories
based on the type of content they deliver. These categories
are:
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Document and productivity
Image viewer
Multimedia
Sound player
Video player
Three-dimensional (3-D) graphics
.
Mozilla Firefox uses a well-developed extension system to
reduce the feature creep that plagued the Mozilla Application
Suite.
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Document and Productivity
Browser Extensions
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
Document and productivity browser
extensions let you use a browser to read
documents, such as PDF files and viewed using
Adobe Acrobat Reader.

If you have Acrobat Reader, a browser can use it
to display and print files with .pdf extensions.

If you have installed Microsoft Office, a browser
can start Word, Excel, and other Office programs
to display files with extensions, such as .doc and
.xls.
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Image Viewer Browser
Extensions
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
Browser extensions from this category let the
browser display graphics, such as interactive road
maps or alternative file formats and viewers for
GIF and JPEG files.

Image viewer plug-ins also display different
picture file formats.

If a Web site indicates you need a specific image
viewer plug-in, you can usually download it at that
time, directly from that site.
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Multimedia Browser
Extensions
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
Multimedia contains browser extensions that
appeal to most of the senses.

The Flash Player lets your Web browser display
simple animations, user interfaces, static graphics,
movies, sound, and text.

The Shockwave Player is a more fully featured
browser plug-in that you must download and
install.
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Sound Player Browser
Extensions
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
Sound player browser extensions, such as
Beatnik, and Real Player, let your Web browser
play sounds.

Real Player is a free plug-in that plays streaming
audio and video files over the Internet.

Beatnik delivers high-quality interactive music
and sound on the Web and in many wireless
devices.
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Video Player Browser
Extensions
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
Video player browser extensions deliver movies to Web
browsers over the Internet.

QuickTime was one of the first movie players developed.
It plays video, sound, music, 3-D, and virtual reality for both
Macintoshes and PCs.

Other widely used movie players include RealPlayer and
Windows Media Player.
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Some of these players download a complete movie before
playing it, while others use streaming technology to play a
movie before it has been completely downloaded.
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3-D Browser Extensions
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
Virtual Reality Modeling Language or VRML is an
Internet programming language that creates threedimensional environments that can mimic known worlds or
define fictional ones.
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With VRML you can navigate and interact with a threedimensional scene.

VRML sites are used for game, product and location tours.
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Extensible 3D (X3D) is the next generation open standard
for 3D on the Web.
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Finding Browser Extensions
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
A good way to locate browser extensions is to visit
a download site such as Tucows.

Many download sites group plug-ins by the
functions they perform, which makes it easy to
view the available plug-ins for the type of files you
want to use.
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Commonly Used
Browser Extensions
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Summary
Department of
Information Technology

There are different types of computer security threats and
some countermeasures that you can take to prevent them.

There are copyright issues related to the information you
locate and use on the Internet.

There are different categories of browser extensions that
you might need as you use the Web.

You should use the security information presented in this
tutorial to create a safe environment in which to enjoy the
Web’s many resources and games on your own computer.
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References & useful sites:
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Department of
Information Technology
Schneider, G. & Evans J. (2004), “The Internet,
New Perspectives”, 5th edition, Course
Technology, Tutorial 8.
www.AdwareReport.com
antivirus.about.com
en.wikipedia.org
https://addons.mozilla.org
www.turnitin.com
www.plagiarism.org
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