Transcript Chapter 5 - Department of Computer Science and Information Systems

Security
Threats and Protection
Mechanisms
Learning Objectives
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Internet security issues (intellectual property
rights, client, communication channels, servers)
Specific security objectives for protecting Web
business assets and customer privacy
How to protect: clients, data in transit, server
computers.
Organizations that promote computer, network,
and Internet security
Security Overview
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Computer security is the protection of assets from
unauthorized access, use, alteration, or destruction
Two types of security:
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Physical security
Logical security
Vocabulary:
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Any act or object that poses a danger to computer assets is
known as a threat
Countermeasure is a procedure that recognizes, reduces, or
eliminates a threat
An eavesdropper is a person or device that can listen in on
and copy Internet transmissions
Aspects of Security
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Three computer security categories:
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Secrecy
Integrity
Availability
Secrecy refers to protecting against unauthorized
data disclosure and ensuring the authenticity of
the data’s source
Integrity refers to preventing unauthorized data
modification
Necessity refers to preventing data delays or
denials
Risk Management
The risk management model shows four general
actions to take according to the severity of a threat
Security Policy
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A security policy is a written statement describing which
assets to protect and why they are being protected, who is
responsible for that protection, and which behaviors are
acceptable and which are not
The first step an organization must take in creating a
security policy is to determine what assets to protect and
from whom
Specific elements of a security policy address the following
points:
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Authentication and access control
Secrecy and data integrity
Audit
Procedures
Security elements in e-commerce
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There are three elements in e-commerce
transactions
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Client
Communication channel
Server
Each element must be protected
Each element has its own requirements
and special characteristics
Threats to the Client
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Active web content, i.e. non-static pages which
contain instructions which execute in the client (for
example: ActiveX, Java Applets, JavaScript, other
plug-ins)
Systems software bugs (e.g. Microsoft RPC bugs have
allowed the proliferation of the Blaster worm)
Software application bugs (e.g. Microsoft Outlook
bugs can be exploited by viruses)
Result: Unauthorized access or control of the client
ActiveX Controls
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ActiveX is an object that contains programs and
properties that Web designers place on Web
pages to perform particular tasks
ActiveX controls run only on computers running
Windows and only on browsers that support them
Because ActiveX controls have full access to client
computers they can cause secrecy, integrity, or
necessity violations
Java Applets
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Java adds functionality to business applications
and can handle transactions and a wide variety
of actions on the client computer
The Java sandbox confines Java applet actions
to a set of rules defined by the security model
These rules apply to all untrusted Java applets
Bugs in the Java VM can cause security
compromises
JavaScript
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JavaScript is a scripting language that
enables Web page designers to build active
content
Errors in JavaScript implementations can
invoke privacy and integrity attacks
JavaScript programs do not operate under
the restrictions of the Java sandbox security
model
Other Active Content
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Plug-ins are programs that interpret or execute
instructions embedded in downloaded graphics,
sounds, and other objects
Popular plug-ins include Macromedia Flash, Microsoft
Media Player and Apple Quicktime.
Active content, including all forms, enables Web
pages to take action
Plug-ins perform their duties by executing commands
buried within the media they are manipulating
Although active content gives life to static Web pages
it also introduces unique challenges for protecting
the client
Viruses
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A virus is software that attaches itself to another
file and can executes when host program is
activated thus bypassing normal authorization
controls
E.g. a MS Word macro virus is coded as a small
program and is embedded in a Word document
Viruses can take any number of actions e.g.
email everyone in the address book or make
phone calls
Viruses often use application software bugs
Client compromises
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Clients can be compromised by exploiting system
software bugs to take over computers
A Trojan horse is a program hidden inside another
program or Web page that masks its true purpose
A worm is a program that has the instructions to
look for and capture other computers on the net
after infecting one
A zombie is a program that secretly takes over
another computer for the purpose of launching
attacks on other computers
Threats to the Communication Channel
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The Internet is the medium over which ecommerce data is transferred
Messages on the Internet travel a random path
from a source node to a destination node
The content of messages is not protected and
anyone on the message path can record its
contents
If communication is sensitive additional measures
must be taken to protect the data
This is a core requirement for e-commerce
Specific Threats
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Secrecy
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Integrity
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Capture user identity preferences or record their
activities
Capture transaction details
Capture payment information
modify transactions
modify user credential (e.g. delivery address)
Availability
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make shop unavailable to customers
Threats to the Server
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Servers have software vulnerabilities that can be
exploited to cause destruction or to acquire
information illegally
E.g. databases connected to the Web contain
information that could damage a company if it
were disclosed or altered
Physical security and access control is also very
important
Threats to Intellectual Property
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Intellectual property is the ownership of ideas
and control over the tangible or virtual
representation of those ideas
IP includes:
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Names, for example trademarks and domain
names (Cybersquatting, name changing, name
stealing)
Digital intellectual property, including art,
logos, and music posted on Web sites, is
protected by laws
Computer Security Resources
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CERT
SANS Institute
Internet Storm Center
Center for Internet Security
U.S. Dept. of Justice Cybercrime
National Infrastructure Protection Center
Protecting Electronic
Commerce Assets
Monitoring Active Content
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Most browsers are equipped to recognize
when they are about to download Web
page containing active content
Users can configure the user of active
content by their browser
For example, configure Java VM using the
Java security console
Microsoft Internet Explorer
Microsoft Internet Explorer
Netscape Navigator
Netscape Navigator
Antivirus Software
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Antivirus software is a defense strategy
Antivirus software matches the contents of a file
under examination against a database of virus
“signatures”
Thus, antivirus software cannot protect against
viruses that have not been discovered earlier and
recorded in the database
One of the most likely places to find a virus is in an
electronic mail attachment
Some Web e-mail systems let users scan attachments
using antivirus software before downloading e-mail
Protecting e-commerce
communications
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Providing e-commerce channel security means:
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Providing channel secrecy
Guaranteeing message integrity
Ensuring channel availability
A complete security plan includes authentication
Businesses must prevent eavesdroppers from
reading the Internet messages that they
intercept
Best available way to do this is via encryption
Encryption
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Encryption is a mathematical technique which
encodes information using a key to transform the
original information into a string of characters
that is unintelligible
The program that transforms text into cipher text
is called an encryption program
At the other end of the communication channel
each message is decrypted using the same or a
related key by a decryption program
Types of Encryption
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Asymmetric encryption or public-key
encryption, encodes messages by using
two mathematically related numeric keys:
a public key and a private key
Symmetric encryption or private-key
encryption, encodes a message using a
single numeric key to encode and decode
data
Hash Functions
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Hash algorithms are one-way functions.
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A hash algorithm has these characteristics:
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It uses no secret key
The message digest it produces cannot be
inverted to produce the original information
The algorithm and information about how it works
are publicly available
Hash collisions are nearly impossible.
MD5 is an example of a hash algorithm
Encryption Methods
Encryption Algorithms and Standards
Secure Sockets Layer (SSL)
Digital Certificates
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A digital certificate verifies that a user or Web
site is who it claims to be
The digital certificate contains a means for
sending an encrypted message to the entity
A Web site’s digital certificate is a shopper’s
assurance that the Web site is the real store
Proof of validity and management of digital
certificates is provided by the certification
authority
Digital Certificates in IE
Ensuring Transaction Integrity
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Integrity violations can occur whenever a
message is altered while in transit
between the sender and receiver
Ensuring transaction integrity, two
separate algorithms are applied to a
message:
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Hash function
Digital signature
Digital Signature
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An encrypted message digest is called a digital
signature
A purchase order accompanied by the digital
signature provides the merchant positive
identification of the sender and assures the
merchant that the message was not altered
Used together, public-key encryption, message
digests, and digital signatures provide quality
security for Internet transactions
Transaction Delivery
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A denial or delay of service attack
removes or absorbs resources
One way to deny service is to flood the
server with a large number of packets
To prevent such attacks, a robust
network architecture should be in place
and network countermeasures should be
in place
Protecting the Web Server
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The e-commerce server which incorporates a Web
server, responds to requests from Web browsers
through the HTTP protocol and CGI scripts
Security measures for commerce servers:
• Access control and authentication
• Operating system controls
• Firewall
Access Control and
Authentication
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Access control and authentication refers to
controlling who and what has access to the ecommerce server
Operating systems often provide access control
list security to restrict file access to selected
users
Users identify themselves using either a
password or a token
An access control list (ACL) is a list or database
of people who can access the files and resources
Firewalls
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A firewall is a system that is installed at
the entry point of a network
The firewall provides the first line of
defense between a network and the
Internet or other network that could pose
a threat
Acting as a filter, firewalls permit selected
messages to flow into and out of the
protected network
Types of Firewalls
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Packet-filter firewalls examine all the
data flowing back and forth between the
trusted network
Application layer firewalls filter traffic
based on the application they request
Proxy severs are firewalls that
communicate with the Internet on the
private network’s behalf
IP Protection
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A watermark is data imperceptibly added to the original
digital asset in order to convey hidden copyright data
A watermark can be used to verify the lawful use of the
asset
It should not reduce the quality of the digital asset
Still in its infancy as a market
Other techniques (less powerful) are based on
mechanisms built-in the hardware or the software
Examples include DVD and MS Media Player but more
often than not can be bypassed