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Chapter 11 Security and Ethics

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Title: Chapter 11 Security and Ethics


1
Chapter 11Security and Ethics
  • Understanding Operating Systems, Fourth Edition

2
Objectives
  • You will be able to describe
  • The role of the operating system with regard to
    system security
  • The effects of system security practices on
    overall system performance
  • The levels of system security that can be
    implemented and the threats posed by evolving
    technologies
  • The differences between computer viruses and
    worms, and how they spread
  • The difficulties of teaching ethics to user
    groups and the role of education in system
    security

3
Role of the Operating System in Security
  • Operating system plays a key role in computer
    system security
  • Any vulnerability at the operating system level
    opens the entire system to attack
  • The more complex and powerful the operating
    system, the more likely it is to have
    vulnerabilities to attack
  • System administrators must be on guard to arm
    their operating systems with all available
    defenses against attack

4
System Survivability
  • Capability of a system to fulfill its mission, in
    a timely manner, in the presence of attacks,
    failures, or accidents
  • Key properties of survivable systems
  • Resistance to attacks
  • Recognition of attacks and resulting damage
  • Recovery of essential services after an attack
  • Adaptation and evolution of system defense
    mechanisms to mitigate future attacks

5
System Survivability (continued)
Table 11.1 Four key properties of a survivable
system
6
Levels of Protection
System administrator must evaluate the risk of
intrusion for each computer configuration, which
in turn depends on the level of connectivity
given to the system
Table 11.2 A simplified comparison of security
protection required for three typical computer
configurations
7
Backup and Recovery
  • Backup and recovery policies are essential for
    most computing systems
  • Many system managers use a layered backup
    schedule
  • Backups, with one set stored off-site, are
    crucial to disaster recovery
  • Written policies and procedures and regular user
    training are essential elements of system
    management

8
Backup and Recovery
  • Written security procedures should recommend
  • Frequent password changes
  • Reliable backup procedures
  • Guidelines for loading new software
  • Compliance with software licenses
  • Network safeguards
  • Guidelines for monitoring network activity
  • Rules for terminal access

9
Security Breaches
  • A gap in system security can be malicious or not
  • Intrusions can be classified as
  • Due to uneducated users and unauthorized access
    to system resources
  • Purposeful disruption of the systems operation
  • Purely accidental
  • Examples Hardware malfunctions, undetected
    errors in OS or applications, or natural
    disasters
  • Malicious or not, a breach of security severely
    damages the systems credibility

10
Unintentional Intrusions
  • Any breach of security or modification of data
    that was not the result of a planned intrusion
  • Examples
  • Accidental incomplete modification of data
  • When nonsynchronized processes access data
    records and modify some but not all of a records
    fields
  • Errors due to incorrect storage of data values
  • e.g., When the field isnt large enough to hold
    the numeric value stored there

11
Unintentional Intrusions (continued)
Figure 11.1 (a) Original data value in a field
large enough to hold it. If the field is too
small, (b) FORTRAN replaces the data with
asterisks, (c) COBOL truncates the higher order
digits and stores only the digits that remain
12
Intentional Attacks
  • Types of Intentional attacks
  • Intentional unauthorized access
  • e.g., denial of service attacks, browsing, wire
    tapping, repeated trials, trap doors, and trash
    collection
  • Viruses and worms
  • Trojan Horses
  • Bombs
  • Blended threats

13
Intentional Unauthorized Access
  • Denial of service (DoS) attacks
  • Synchronized attempts to deny service to
    authorized users by causing a computer to perform
    repeated unproductive task
  • Browsing
  • Unauthorized users gain access to search through
    secondary storage directories or files for
    information they should not have the privilege to
    read

14
Intentional Unauthorized Access (continued)
  • Wire Tapping Unauthorized users monitor or
    modify a users transmission
  • Passive wire tapping Refers to just listening to
    the transmission but not changing the contents,
    and reasons include
  • To copy data while bypassing any authorization
    procedures
  • To collect specific information such as password
  • Active wire tapping Data being sent is modified
  • Methods include between lines transmission and
    piggyback entry

15
Intentional Unauthorized Access (continued)
  • Repeated Trials To enter systems by guessing
    authentic passwords
  • Trap doors An unspecified and undocumented entry
    point to the system
  • Installed by a system diagnostician or programmer
    for future use
  • Leaves the system vulnerable to future intrusion
  • Trash collection Use of discarded materials such
    as disks, CDs, printouts, etc., to enter the
    system illegally

16
Intentional Unauthorized Access (continued)
Table 11.3 Average time required to guess
passwords up to ten alphabetic characters (A-Z)
using brute force
17
Intentional Unauthorized Access (continued)
  • Malicious attacks on computers may violate state
    and federal law under the Federal Computer Fraud
    and Abuse Act of 1986
  • Those convicted have been sentenced to
    significant fines and jail terms, as well as
    confiscation of their computer equipment
  • In the U.S., attempts to intrude into your system
    should be reported to the FBI

18
Viruses
  • Small programs written to alter the way a
    computer operates, without permission of the user
  • Must meet two criteria It must be self-executing
    and self-replicating
  • Usually written to attack a certain operating
    system
  • Spread via a wide variety of applications
  • Macro virus works by attaching itself to a
    template (such as NORMAL.DOT), which in turn is
    attached to word processing documents

19
Viruses (continued)
Figure 11.2 A file infector virus attacks a
clean file (a) by attaching a small program to it
(b)
20
Viruses (continued)
Table 11.4 Types of viruses
21
Viruses (continued)
Table 11.4 (continued) Types of viruses
22
Worms and Trojan Horses
  • Worm A memory-resident program that copies
    itself from one system to the next without
    requiring the aid of an infected program file
  • Results in slower processing time of real work
  • Especially destructive on networks
  • Trojan Horse A destructive program thats
    disguised as a legitimate or harmless program
  • Allows the programs creator to secretly access
    users system

23
Bombs and Blended Threats
  • Logic bomb A destructive program with a fuse a
    certain triggering event (such as a keystroke or
    connection with the Internet)
  • Spreads unnoticed throughout a network
  • Time bomb A destructive program triggered by a
    specific time, such as a day of the year
  • Blended Threat Combines into one program the
    characteristics of other attacks
  • e.g., including a virus, worm, Trojan Horse,
    spyware, and other malicious code into a single
    program

24
Blended Threats (continued)
  • Blended Threats (continued)
  • Characteristics of blended threat
  • Harms the affected system
  • Spreads to other systems using multiple methods
  • Attacks other systems from multiple points
  • Propagates without human intervention
  • Exploits vulnerabilities of target systems
  • Protection Combination of defenses in
    combination with regular patch management

25
System Protection
  • No single guaranteed method of protection
  • System vulnerabilities include
  • File downloads, e-mail exchange
  • Vulnerable firewalls
  • Improperly configured Internet connections, etc.
  • Need for continuous attention to security issues
  • System protection is multifaceted and protection
    methods include
  • Use of antivirus software, firewalls, restrictive
    access and encryption

26
Antivirus Software
  • Software to combat viruses can be preventive,
    diagnostic, or both
  • Preventive programs may calculate a checksum for
    each production program
  • Diagnostic software compares file sizes, looks
    for replicating instructions or unusual file
    activity
  • Can sometimes remove the infection and leave the
    remainder intact
  • Unable to repair worms, Trojan horses, or blended
    threats as they are malicious code in entirety

27
Antivirus Software (continued)
Table 11.5 Websites containing current
information on systems security
28
Antivirus Software (continued)
Figure 11.4 (a) Uninfected file (b) file
infected with a virus (c) a Trojan horse or worm
consists entirely of malicious code
29
Firewalls
  • A set of hardware and/or software designed to
    protect a system by disguising its IP address
    from unauthorized users
  • Sits between the Internet and network
  • Blocks curious inquiries and potentially
    dangerous intrusions from outside the system
  • Mechanisms used by the firewall to perform
    various tasks include
  • Packet filtering
  • Proxy servers

30
Firewalls (continued)
Figure 11.5 Firewall sitting between campus
networks and Internet, filtering
requests for access
31
Firewalls (continued)
  • Typical tasks of the firewall are to
  • Log activities that access the internet
  • Maintain access control based on senders or
    receivers IP addresses
  • Maintain access control based on services that
    are requested
  • Hide internal network from unauthorized users
  • Verify that virus protection is installed and
    enforced
  • Perform authentication based on the source of a
    request from the Internet

32
Firewalls (continued)
  • Packet filtering
  • Firewall reviews header information for incoming
    and outgoing Internet packets to verify
    authenticity of source address, destination
    address, and protocol
  • Proxy server
  • Hides important network information from
    outsiders by making network server invisible
  • Determines if request for access to the network
    is valid
  • Proxy servers are invisible to users but are
    critical to the success of the firewall

33
Authentication
  • Authentication A verification that an individual
    trying to access a system is authorized to do so
  • Kerberos A network authentication protocol
  • Need for password encryption to improve network
    security led to development of Kerberos
  • Designed to provide strong authentication for
    client/server applications
  • Uses strong cryptography
  • Requires systematic revocation of access rights
    from clients who no longer deserve to have access

34
Authentication (continued)
Figure 11.6 Using Kerberos, when client A
attempts to access server B, user is
authenticated (a) and receives a ticket for the
session (b). Once the ticket is issued, client
and server can communicate at will (c). Without
the ticket, access is not granted
35
Encryption
  • Most extreme protection method for sensitive data
    where data is put into a secret code
  • To communicate with another system, data is
    encrypted, transmitted, decrypted, and processed
  • Sender inserts public key with the message
  • Message receiver required to have private key to
    decode the message
  • Disadvantages
  • Increases systems overhead
  • System becomes totally dependent on encryption
    process itself

36
Sniffers and Spoofing
  • Sniffers Programs that reside on computers
    attached to the network
  • Peruse data packets as they pass by, examine each
    one for specific information
  • e.g., Particularly problematic in wireless
    networks
  • Spoofing Assailant fakes IP addresses of an
    Internet server by changing the address recorded
    in packets it sends over the Internet
  • Used when unauthorized users want to disguise
    themselves as friendly sites

37
Password Management
  • Most basic techniques used to protect hardware
    and software investments include
  • Good passwords
  • Careful user training
  • Password Construction
  • Good password is unusual, memorable, and changed
    often
  • Password files normally stored in encrypted form
  • Password length has a direct effect on the
    ability of password to survive password cracking
    attempts

38
Password Construction (continued)
Figure 11.8 Password verification flowchart
39
Password Construction (continued)
Table 11.6 Number of combinations of passwords
depending on their length and available character
set
40
Password Construction (continued)
  • Reliable techniques for generating a good
    password
  • Use minimum of eight characters, including
    numbers and nonalphanumeric characters
  • Create a misspelled word or join bits of phrases
    into a word thats easy to remember
  • Follow a certain pattern on the keyboard
  • Create acronyms from memorable sentences
  • Use upper and lowercase characters if allowed
  • Never use a word thats included in any dictionary

41
Password Construction (continued)
  • Dictionary attack A method of breaking encrypted
    passwords
  • Requirements
  • A copy of the encrypted password file
  • Algorithm used to encrypt the passwords
  • Prevention
  • Some operating systems salt user passwords with
    extra random bits to make them less vulnerable to
    dictionary attacks

42
Password Alternatives
  • Use of a smart card
  • A credit card-sized calculator that requires both
    something you have and something you know
  • Displays a constantly changing multidigit number
    synchronized with an identical number generator
    in the system
  • User must type in the number that appears at that
    moment on the smart card
  • For added protection, user then enters a secret
    code
  • User is admitted to the system only if both
    number and code are validated

43
Password Alternatives (continued)
  • Biometrics
  • The science and technology of identifying
    individuals based on unique biological
    characteristics of each person
  • Current research focuses on
  • Analysis of the human face, fingerprints, hand
    measurements, iris/retina, and voice prints
  • Positively identifies the person being scanned
  • Critical factor is reducing the margin of error
  • Presently, biometric authentication is expensive

44
Social Engineering
  • A technique whereby system intruders gain access
    to information about a legitimate user to learn
    active passwords by
  • Looking in and around the users desk for a
    written reminder
  • Trying the user logon ID as the password
  • Searching logon scripts
  • Telephoning friends and co-workers to learn the
    names of users family members, pets, vacation
    destinations, favorite hobbies, car model, etc.

45
Social Engineering (continued)
  • Phishing Intruder pretends to be a legitimate
    entity and contacts unwary users asking them to
    reconfirm their personal and/or financial
    information
  • Example 2003 incident involving eBay customers
  • Default passwords
  • Pose unique vulnerabilities because they are
    widely known
  • Routinely shipped with hardware or software
  • Routinely passed from one hacker to the next
  • Should be changed immediately

46
Ethics
  • Ethical behavior Be good. Do good.
  • IEEE and ACM issued a standard of ethics in 1992
  • Apparent lack of ethics in computing is a
    significant departure from other professions
  • Consequences of ethical lapses
  • Illegally copied software can result in lawsuits
    and fines
  • Plagiarism is illegal and punishable by law
  • Eavesdropping on e-mail, data, or voice
    communications is sometimes illegal and usually
    unwarranted

47
Ethics (continued)
  • Consequences of ethical lapses (continued)
  • Cracking (malicious hacking) causes systems
    owner and users to question the validity of
    systems data
  • Unethical use of technology is clearly the wrong
    thing to do
  • Specific activities to teach ethics can include
  • Publish policies that clearly state which actions
    will and will not be condoned
  • Teach a regular seminar on the subject including
    real-life case histories
  • Conduct open discussions of ethical questions

48
Summary
  • Cant overemphasize the importance of keeping the
    system secure
  • System is only as good as the integrity of the
    data thats stored on it
  • A single breach of security whether
    catastrophic or not, whether accidental or not
    damages the systems integrity
  • Damaged integrity threatens the viability of the
    best-designed system, its managers, its
    designers, and its users
  • Vigilant security precautions are essential
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