Transcript Computer and Information Security

Computer and Information
Security
Chapter 1
Introduction
Slides by H. Johnson & S. MalladiModified by SJF-S'06
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Overview
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Security Goals
The need for security
OSI Security Architecture
Attacks, services and mechanisms
Security attacks
Security services
Methods of Defense
A model for Internetwork Security
Internet standards and RFCs
Security Goals
Confidentiality
Integrity
Avalaibility
Security Goals
• Confidentiality
– Concealment of information or resources
• Integrity
– Trustworthiness of data or resources
• Availability
– Ability to use information or resources
Confidentiality
• Need for keeping information secret
arises from use of computers in
sensitive fields such as government
and industry
• Access mechanisms, such as
cryptography, support confidentiality
– Example: encrypting income tax return
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
• Includes both correctness and trustworthiness
Availability
• Is an aspect of reliability and system
design
• Attempts to block availability, called
denial of service attacks are difficult
to detect
– Example: bank with two servers –one is
blocked, the other provides false
information
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 needed
to protect data during their
transmission
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
information (immigration databases, flight tickets, stock
markets etc.)
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
– Can I ever stay relaxed that no hacker can enter my
network and play havoc?
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
before they deliver the product to me
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
– In fact, insider attacks are greater both in
terms of likelihood of happening and damage
caused
https://
(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 play.
The only way to avoid attacks is to keep up-to-date with
latest trends and stay ahead of malicious netizens
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
– Certainly not all
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 telecommunications and to Open
system Interconnection (OSI)
OSI Network Stack and Attacks
(V. Shmatikov)
application
email,Web,NFS
presentation
session
transport
network
data link
RPC
TCP
IP
802.11
Sendmail, FTP, NFS bugs,
chosen-protocol and
version-rollback attacks
RPC worms, portmapper exploits
SYN flooding, RIP attacks,
sequence number prediction
IP smurfing and other
address spoofing attacks
WEP attacks
physical
Only as secure as the single weakest layer…
7 Layer Model
Layer
Functions
7
Application
How application uses network
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How to represent & display data
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Presentatio
n
Session
4
Transport
3
Network
2
Data Link
1
Physical
How to provide reliable delivery (error
checking, sequencing, etc.)
How addresses are assigned and packets
are forwarded
How to organize data into frames &
transmit
How to transmit “bits”
How to establish communication
Attacks, Services and
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 service makes use of one or more
security mechanisms
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
communication line
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
legitimate and authentic party
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 security
services and violate the security
policy of a system.
Threats
• Disclosure – unauthorized access to
information
• Deception – acceptance of false data
• Disruption- interruption or prevention
of correct operation
• Usurpation- unauthorized control of
some part of a system
Examples of Threats
• Snooping intercepting information
(“passive” wiretapping)
• Modification or alteration of
information by “active” wiretapping
• Masquerading or spoofing
• Repudiation of origin
• Delay or denial of service
Safeguards and
Vulnerabilities
• A Safeguard is a countermeasure to
protect against a threat
• A weakness in a safeguard is called a
vulnerability
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
• Launch denial of service attacks
Passive Attacks
Passive Attacks
Active Attacks
Active Attacks
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.
– E.g. disabling authentication
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
– Morris Internet worm spread to 5% of machines on the
Internet, 1988
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
– E.g. encryption, cryptographic protocols
Security Services
• A security service is a service provided
by the protocol layer of a
communicating system (X.800)
• 5 Categories
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Authentication
Access Control
Data confidentiality
Data Integrity
Nonrepudiation (and Availability)
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
– Virus that deletes files
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
– Protection against denial-of-service
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
• E.g. security audit trail
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
• May need a trusted third part to assist
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)
• Physical Controls
Internet standards and
RFCs
• The Internet society
– Internet Architecture Board (IAB)
– Internet Engineering Task Force (IETF)
– Internet Engineering Steering Group
(IESG)
Internet RFC Publication Process
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.
• Jimmy McGibney, IT Security 2004/2005, WIT.