Tutorial.06

Report
Tutorial 6:
Internet Security
Objectives
• Session 6.1
– Explore basic security concepts and
countermeasures
– Study how encryption works
– Learn about phishing and digital watermarking
– Understand denial-of-service attacks and how to
prevent them
– Recognize and prevent identity theft
– Explore security concerns for users of social
networks
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Objectives
• Session 6.2
– Understand security threats to Web clients and
how to prevent them
– Investigate the use of programs that detect and
remove malware
– Recognize the potential security issues that arise
from electronic tracking devices
– Study how a firewall is used to block
communication
– Learn how to secure a Web server
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Session 6.1 Overview
Physical and Logical Security
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Security Basics
• Security is broadly defined as the protection of assets
from unauthorized access, use, alteration, or destruction
• Any act or object that endangers an asset is known as a
threat
• Logical security threats are generally classified in three
categories:
– Secrecy threat – occurs when data is disclosed to an
unauthorized party
– Integrity threat – results in unauthorized data
modification
– Necessity threat – causes data delays or denials
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Security Basics
• A countermeasure is a physical or logical procedure that
recognizes, reduces, or eliminates a threat
• The countermeasure that an individual or organization
chooses often depends on the expected types of threats
– The best way to safeguard against a threat is to
prevent it from occurring in the first place
– In some cases, need to plan for losses in service or
theft by purchasing insurance or installing backup
systems
• The process of risk management focuses on identifying
threats and determining available and affordable
countermeasures
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Using Encryption to Protect
Against Secrecy Threats
• Secrecy threats are the best known of the logical security
categories
• The study of ways to secure information is called
cryptography
• Encryption is the process of coding information using an
algorithm to produce a string of characters that is unreadable
• An algorithm is a formula or set of steps that solves a
particular problem
• Some algorithms also use a key, which is a fact that the
encryption algorithm uses as part of its formula
• The process of using a key to reverse encrypted text is called
decryption
• Encrypted information is called cipher text, whereas
unencrypted information is called plain text
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Using Encryption to Protect
Against Secrecy Threats
• Private-key encryption (also called symmetric
encryption) uses a private key, or common key,
known by both the sender and receiver
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Using Encryption to Protect
Against Secrecy Threats
• With public-key encryption (also called asymmetric
encryption), a person has a private key (also referred
to as secret key) known only to one party, and a
public key known to everyone
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Using Encryption to Protect
Against Secrecy Threats
• Encryption is considered weak or strong based on its
algorithm and the number of characters in the
encryption key
• Resistance of an encrypted message to attack
attempts depends on the size of the key used
– A 40-bit key provides a minimal level of security
– 128-bit and 256-bit keys are commonly called
strong keys
• As computers become faster and more powerful, the
length of keys must increase to prevent computers
from being used to break encrypted transmissions
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Protecting the Integrity of
Electronic Data
• Data integrity threats can change the actions an individual or
organization takes by altering the content of a message or
transaction
• Occurs when an unauthorized party alters data during its transfer or
while it is stored on a drive or server
• In a man-in-the-middle exploit, the contents of an email are
changed in a way that negates the message’s original meaning
• Phishing Attacks
– An email that includes the name of someone you know in the
message’s From line, a tactic called spoofing
– Often spoofed email from banks, online services, credit card
companies, etc.
– When individuals open the email and follow a hyperlink, they
are taken to a form that illicitly collects personal information
– Called phishing because it “fishes” for information
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Protecting the Integrity of
Electronic Data
• Phishing Attacks (continued)
– Receiving the message is usually not harmful; the
recipient must follow instructions in the message
or click an included hyperlink to become a victim
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Protecting Copyrighted Materials
Using Digital Watermarks
• A digital watermark is a digital pattern containing
copyright information that is inserted into a digital
image, animation, or audio or video file
– The watermark is inserted using a software
program so that it is invisible and undetectable
– To view the watermark, a software program
unlocks it, retrieving the information it stores
• Steganography is a process that hides encrypted
messages within different types of files
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Preventing Denial-of-Service Attacks
• The most common necessity attack, called a denial
of service (DoS) attack, occurs when an attacker
floods a computer, server, or network with so many
messages that the network’s bandwidth resources
are consumed disabling its services and
communications
• In a distributed denial of service (DDoS) attack, the
attacker uses a large number of computers that each
launch a DoS attack on a server at the same time
• Often computers used in a DDoS attack are ones that
have been hijacked by a Trojan horse; these
computers are often called bots or zombies
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Preventing Denial-of-Service Attacks
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Preventing Denial-of-Service Attacks
• To prevent an attack, different types of hardware and
software can be installed that monitor and detect
problems early and prevent attacks
– A company can defend its Web server by installing
a denial-of-service filter, or DoS filter
– DoS filter functions are often included as part of a
network software tool called a packet sniffer,
which examines the structure of the data
elements that flow through a network
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Recognizing and Preventing
Identity Theft
• A thief can potentially steal a person’s entire identity
• In this type of crime, called identity theft, a thief can:
– Use the victim’s personal information to open
bank accounts, obtain new credit cards, and buy
expensive goods on credit
– Damage the victim’s credit rating
– Make transactions for which the victim is
responsible
• It can take a long time for victims to clear their
records and restore their credit
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Recognizing and Preventing
Identity Theft
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Security Concerns for
Social Network Users
• As use of social networks increase, individuals and
business must implement appropriate security strategies
to protect themselves from problems and threats
• Carefully control the information posted on a social
networking site and use security settings that offer the
most protection
• Rely on common sense to protect identity, property, and
privacy; many hoaxes and scams start on social
networking sites
• Be alert for the potential security problems that a
shortened URL can cause
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Session 6.2 Overview
Enhancing Security
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Web Client Security
• One of the most important Web client security risks arises
from the existence of active content
• Active Content: Java, JavaScript, and ActiveX
– One of the most dangerous entry points for DoS attacks is
from programs that travel with applications to a browser
and are executed on the user’s computer
– These programs, often called active content, include Java,
JavaScript, and ActiveX components that can run programs
on a Web client
– Active content components can:
• Make Web pages more useful by providing interactive
content (i.e., calculating shipping costs, creating
mortgage payment tables, creating animation)
• Be used for malicious purposes
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Web Client Security
• Active Content: Java, JavaScript, and ActiveX (cont.)
– A Java applet is a program written in the Java
programming language which can execute and consume
computer resources
– A JavaScript program can pose a threat because it can run
without being compiled
– ActiveX controls are Microsoft’s technology for writing
small applications that perform some action in Web pages;
these controls have access to a computer’s file system
– Internet Explorer secures ActiveX controls with a digital
signature which provides verification of the contents of
the file and identifies its author or developer
– When a digital signature authenticates an ActiveX control’s
developer or source, it is called a signed ActiveX control
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Detecting and Removing Malware
• Malware, a term that means “malicious software,” is
a category of software that is installed without the
user’s consent
• A virus is a program that replicates itself with the
goal of infecting other computers
• A Trojan horse is a program hidden inside another
program
• A worm is a self-replicating and self-executing
program that sends copies of itself to other
computers over a network
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Detecting and Removing Malware
• Adware (short for “ad-supported software”) is a category
of software that includes advertisements to help pay for
the program in which they appear
• When adware is installed on a computer without the
user’s knowledge and consent it becomes a form of
malware called spyware
• Spyware works much like adware except that the user
has no control over of knowledge of the ads and other
monitoring features the ads contain
• Internet security software can prevent the spread of
malware by blocking them from being downloaded from
the server
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Detecting and Removing Malware
• Two vendors that provide a full range of products are
Norton and McAfee
• Because malware is often hidden in other programs,
running an Internet security program might not
adequately protect your computer
• You can purchase a separate software program that
scans your entire hard drive for malware and
includes tools to remove it
• Lavasoft Ad-Aware Free is a popular program for
scanning for adware
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Blocking Tracking Devices
in Electronic Communications
• A Web bug is a small, hidden graphic on a Web page or in an
email message; it is designed to:
– Work in conjunction with a cookie to obtain information
about the person viewing the page or message
– Send that information to a third party
• Because a Web bug is usually created with a GIF file, it is
sometimes called a clear GIF or a transparent GIF; it is
designed to be hidden on the Web page in which it appears
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Blocking Tracking Devices
in Electronic Communications
• DoubleClick is a division of Google that develops
tools for Internet marketing and advertising
• When a user loads a Web page that contains a Web
bug, their IP address, the last Web site visited, and
other information about the use of the site in which
the clear GIF has been embedded can be recorded
• The GIF file is not visible because it is transparent
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Blocking Tracking Devices
in Electronic Communications
• When you first access a DoubleClick member’s Web site,
DoubleClick uses a cookie to assign you a number and record it
• When you visit any DoubleClick member’s Web site in the
future, DoubleClick reads the cookie and gets your
identification number
• As you use your browser, DoubleClick can use its cookie to
collect information and sell this to its members so they can
customize their Web sites with tailored advertising
• A Web bug is an example of spyware because the clear GIF and
its actions are hidden from the user; while not illegal but it
does create privacy concerns
• You can prevent Web sites from writing cookies by changing
your browser’s settings; when you disable cookies, you lose
some of the positive attributes that cookies can provide
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Blocking Communication
Using a Firewall
• The computer version of a firewall is a software program or
hardware device that controls access between two networks
or between the Internet and a computer
– Can be used on both Web servers and Web clients
– A Web client firewall might be a dedicated hardware
device or a program running on a computer
• Most Internet traffic is harmless; but without protection, an
authorized party can gain access to a computer through a port
• A port on a computer is like a door: It permits traffic to leave
and enter a computer
– When a port is closed, traffic can’t leave or enter the
computer
– The port might be a hardware interface or it might be a
virtual port that handles different kinds of information
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Blocking Communication
Using a Firewall
• Virtual ports use numbers to isolate traffic by type
• A computer has more than 65,000 virtual ports for
different processes such as:
– HTTP/World Wide Web traffic (port 80)
– FTP traffic (port 21)
– SMTP email (port 25)
– POP3 email (port 110)
– SSL (port 443)
• To connect to the Internet, you must open port 80
• If port 80 is not properly protected, an authorized party
can use port 80 or other virtual ports to access your
computer
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Blocking Communication
Using a Firewall
• A firewall can control incoming traffic by rejecting it
unless you have configured it to accept the traffic
• During a port scan, one computer tests all or some of the
ports of another computer to determine whether its
ports are:
– Open – traffic is not filtered and the port permits
entry through it
– Closed – the port does not accept traffic, but a cracker
could use this port to gain entry to and analyze your
computer
– Stealth – the port might be open or closed, but
permits no entry through it
• You can run a port scan by visiting a Web site that offers
this service.
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Blocking Communication
Using a Firewall
• Most firewalls are installed to prevent traffic from
entering the network, but firewalls can also prevent
data from leaving the network
• Especially useful for controlling the activities of
hidden programs that are designed to compromise
the security of a computer
• Because the primary function of a firewall is to block
unwanted traffic from reaching the network it
protects, each organization that installs a firewall
needs to determine what kind of traffic to block and
what kind of traffic to permit
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Communication Channel Security
• Authentication is a general term for the process of
verifying the identity of a person, computer, or
server with a high degree of certainty
• To help keep track of their login information for
different computers and Web sites, some people use
a program called a password manager, which stores
login information in an encrypted form
• A brute force attack occurs when a hacker uses a
program to enter character combinations until the
system accepts a user name and password
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Communication Channel Security
• The combination of a user login plus a password is
called single-factor authentication because it uses
one factor; in this case, something the user knows
• Multifactor authentication relies on more than one
factor
• Another approach that banks and financial
institutions use to add security to online transactions
is multiple layers of control
• Multiple layers of control can be implemented by
using more than one authentication method
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Communication Channel Security
• Digital and Server Certificates
– A digital certificate is an encrypted and passwordprotected file that contains sufficient information to
authenticate and prove a person’s or an organization’s
identity
– Usually, a digital certificate contains the following
information:
• The certificate holder’s name, address, and email
address
• A key that “unlocks” the digital certificate
• The certificate’s expiration date or validity period
• Verification from a trusted third party, called a
certificate authority (CA)
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Communication Channel Security
• Digital and Server Certificates (continued)
– There are two types of digital certificates
• Individuals can purchase one type called a
digital ID; purchasers of digital IDs can use
them to identify themselves to other people
and to Web sites that are set up to accept
digital certificates
• A server certificate is installed on a Web server
to prove the identity of the server to Web
clients that connect to it to conduct
transactions
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Communication Channel Security
• Assurance Providers
– An assurance provider is a third party that, for a fee,
will certify that a person or an organization has met
some criteria for conducting safe transactions and
ensuring privacy before issuing the right to use the
assurance provider’s seal on a Web site
– Examples include:
• The Better Business Bureau’s BBB Accredited
Business Seal (formerly BBBOnLine) certification
program
• The TRUSTe program focuses on privacy issues
• The Norton Secured Seal (formerly VeriSign)
provides a range of services to electronic
commerce Web sites
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Secure Sockets Layer (SSL) and
Transport Layer Security (TLS)
• Secure Sockets Layer (SSL) was the first widely used
protocol for establishing secure, encrypted connections
between Web browsers and Web servers on the Internet
– SSL was revised several times and is still used today
– In 1999, SSL version 3 was improved and reissued by
the Internet Engineering Task Force
– This improved protocol is called Transport Layer
Security (TLS)
• Both SSL and TLS automatically provide a security
“handshake” when a browser and the server to which it
is connected want to participate in a secure connection
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Secure Sockets Layer (SSL) and
Transport Layer Security (TLS)
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Secure Sockets Layer (SSL) and
Transport Layer Security (TLS)
• SSL and TLS both use a public key to encrypt a private key
and send it from the Web server to the browser
• Once the browser decrypts the private key, it uses that
private key to encrypt information sent to the Web
server during the SSL/TLS connection because private-key
encryption is faster than public-key encryption
• When the user leaves the secure Web site, the browser
terminates the SSL/TLS connection and discards these
temporary keys, or session keys
• Session keys exist only during a single connection
(session) between a browser and a server
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Secure Sockets Layer (SSL) and
Transport Layer Security (TLS)
• A growing concern that fraudulent Web sites might
have obtained SSL certificates led a group of
certificate authorities to develop a more stringent set
of verification steps
• In 2008, this development led to the establishment
of stricter criteria and an assurance of a more
consistent application of verification procedures
• Certificate authorities that followed these more
extensive verification procedures were permitted to
issue a new type of certificate called Secure Sockets
Layer-Extended Validation (SSL-EV)
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