Slides by H. Johnson & S. Malladi- Modified by SJF-S '06
1
Computer and Information
Security
Overview
•
Security Goals
•
The need for security
•
OSI Security Architecture
•
Attacks, services and mechanisms
•
Security attacks
•
Security services
•
Methods of Defense
Security Goals
Security Goals
Integrity
Confidentiali ty
Security Goals
• Confidentiality
–
Concealment of information or
resources
• Integrity
–
Trustworthiness of data or resources
• Availability
Confidentiality
•
Need for keeping information secret
arises from use of computers in
sensitive fields such as government
and industry
•
Access mechanisms, such as
Integrity
•
Often requires preventing unauthorized
changes
•
Includes data integrity (content) and origin
integrity ( source of data also called
authentication)
•
Include prevention mechanisms and detection
mechanisms
– Example: Newspaper prints info leaked from White House and gives wrong source
Availability
•
Is an aspect of reliability and
system design
•
Attempts to block availability,
called
denial of service attacks
are
difficult to detect
The Need for Security
•
Computer Security
- the
collection of tools designed
–
to protect data and
–
to thwart hackers
•
Network security or internet
security-
security measures
Security
• Motivation: Why do we need security?
• Increased reliance on Information technology with or with out the use of networks
• The use of IT has changed our lives drastically.
• We depend on E-mail, Internet banking, and several other governmental activities that use IT
• Increased use of E-Commerce and the World wide web on the Internet as a vast repository of various kinds of
Security Concerns
• Damage to any IT-based system or activity can result in severe disruption of services and losses • Systems connected by networks are more prone
to attacks and also suffer more as a result of the attacks than stand-alone systems (Reasons?)
• Concerns such as the following are common
– How do I know the party I am talking on the network is
really the one I want to talk?
– How can I be assured that no one else is listening and learning the data that I send over a network
Concerns continued…
•
Is the web site I am downloading
information from a legitimate one, or a
fake?
•
How do I ensure that the person I just did a
financial transaction denies having done it
tomorrow or at a later time?
•
I want to buy some thing online, but I don’t
want to let them charge my credit card
That is why…
•
..we need security
– To safeguard the confidentiality, integrity,
authenticity and availability of data transmitted over insecure networks
– Internet is not the only insecure network in this world
– Many internal networks in organizations are prone to insider attacks
(V.Shmatikov)
However, in reality
• Security is often over looked (not one of the top criteria)
• Availability, efficiency and performance tend to be the ones
• Buggy implementations
• Systems too complex in nature and rich in features can be filled with security holes
• Incorporation of security into networks, not growing with the rapidly growing number and size of networks
• Attacking is becoming so common and easy – there are books clearly explaining how to launch them
• Security and attacks are a perpetual cat-and-mouse
The Good News...
•
There a lot of techniques for defense
•
Educating people on security solves
many problems
•
About threats and on the existence of
security mechanisms, qualified
personnel, usability and economics
•
We will study a lot of network
defenses
OSI Security
Architecture
•
ITU-T Recommendation X.800
Security Architecture for OSI
•
International Telecommunications
Union (ITU) is a United Nations
sponsored agency that develops
standards relating to
OSI Network Stack and Attacks
(V. Shmatikov)
application presentation session transport network data link physical IP TCP email,Web,N FS RPC 802.11Sendmail, FTP, NFS bugs, chosen-protocol and
version-rollback attacks
SYN flooding, RIP attacks, sequence number prediction IP smurfing and other
address spoofing attacks
RPC worms, portmapper exploits
WEP attacks
7 Layer Model
Layer
Functions
7 Application How application uses network 6 Presentatio
n How to represent & display data 5 Session How to establish communication
4 Transport How to provide reliable delivery (error checking, sequencing, etc.)
3 Network How addresses are assigned and packets are forwarded
2 Data Link How to organize data into frames & transmit
Attacks, Services and
Attacks, Services and
Mechanisms
Mechanisms
•
Security Attack:
Any action that
compromises the security of information.
•
Security Mechanism:
A mechanism
that is designed to detect, prevent, or
recover from a security attack.
•
Security Service:
A service that
enhances the security of data processing
systems and information transfers. A
Security Attacks
Security Attacks
Security Attacks
•
Interruption:
This is an attack on
availability
–
Disrupting traffic
–
Physically breaking communication line
•
Interception:
This is an attack on
confidentiality
–
Overhearing, eavesdropping over a
Security Attacks
(continued)
•
Modification:
This is an attack on
integrity
–
Corrupting transmitted data or
tampering with it before it reaches its
destination
•
Fabrication:
This is an attack on
authenticity
–
Faking data as if it were created by a
Threats and Attacks
•
Threat
- a potential for violation of
security or a possible danger that
might exploit a vulnerability
•
Attack
- an assault on system
security- an intelligent act that is a
deliberate attempt to evade
Threats
• Disclosure
– unauthorized access to
information
• Deception
– acceptance of false data
• Disruption
- interruption or
prevention of correct operation
Examples of Threats
•
Snooping intercepting information
(“passive” wiretapping)
•
Modification or alteration of
information by “active” wiretapping
•
Masquerading or spoofing
•
Repudiation of origin
Safeguards and
Vulnerabilities
•
A
Safeguard
is a countermeasure to
protect against a threat
•
A weakness in a safeguard is called a
Passive and active attacks
•
Passive attacks
– No modification of content or fabrication
– Eavesdropping to learn contents or other information (transfer patterns, traffic flows etc.)
•
Active attacks
– Modification of content and/or participation in communication to
• Impersonate legitimate parties • Modify the content in transit
Two types of threats
• Information access threats
– Intercept or modify data on behalf of users who should not have access to that data.
– E.g. corruption of data by injecting malicious code
• Service threats
– Exploit service flaws in computers to inhibit use by legitimate uses.
Fundamental threats
[McGibney04]
• Information leakage
– Disclosure to unauthorized parties
– Prince Charles mobile phone calls, 1993
• Integrity violation
– Corruption of data or loss of data
– Coca-Cola website defaced with slogans, 1997
• Denial of service
– Unavailability of system/service/network
– Yahoo!, 2000, 1Gbps
• Illegitimate use
Services and Mechanisms
•
A
security
policy
is a statement of
what is and what is not allowed.
•
A
security
service
is a measure to
address a threat
– E.g. authenticate individuals to prevent unauthorized access
•
A
security
mechanism
is a means to
provide a service
Security Services
•
A security service is a service
provided by the protocol layer of a
communicating system (X.800)
•
5 Categories
–
Authentication
–
Access Control
–
Data confidentiality
–
Data Integrity
Security Services
Security Services
• Authentication (who created or sent the data) • Access control (prevent misuse of resources) • Confidentiality (privacy)
• Integrity (has not been altered)
• Non-repudiation (the order is final)
• Availability (permanence, non-erasure) – Denial of Service Attacks
Security Services
Examples
• Authentication
– Ensuring the proper identification of entities and origins of data before communication
• Access control
– Preventing unauthorized access to system resources
• Data confidentiality
– Preventing disclosure to unauthorized parties
• Data integrity
– Preventing corruption of data
• Non-repudiation
– Collecting proof to prevent denial of participation in transaction or communication
• Availability
Security Mechanisms
Examples
•
Two types
– Specific mechanisms existing to provide certain security services
• E.g. encryption used for authentication
– Pervasive mechanisms which are general mechanisms incorporated into the system and not specific to a service
Model for Network
Security
•
Basic tasks
–
Design an algorithm that opponent cannot
defeat
–
Generate the secret information to be
used with the algorithm
–
Develop methods for distributing secret
information
–
Specify a protocol to be used
Methods of Defense
Methods of Defense
• Encryption
• Software Controls
– (access limitations in a data base, in operating system protect each user from other users)
• Hardware Controls
– (smartcard)• Policies
– (frequent changes of passwords)
Internet standards and
Internet standards and
RFCs
RFCs
•
The Internet society
–
Internet Architecture Board (IAB)
–
Internet Engineering Task Force (IETF)
Internet RFC Publication Process
Recommended Reading
Recommended Reading
• Pfleeger, C. Security in Computing. Prentice Hall, 1997.
• Mel, H.X. Baker, D. Cryptography Decrypted. Addison Wesley, 2001
.
• Rita Summers, Secure Computing: Threats and Safe Guards, McGrawHill.
• Peter Ryan and Steve Schneider, Modeling and analysis of security protocols, Addison Wesley.
• V. Shmatikov, Network security and privacy, University of Texas, Austin, TX.
