Chapter 11 Security and Ethics

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Chapter 11Security and Ethics

• Understanding Operating Systems, Fourth Edition

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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

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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
  defences against attack

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System Survivability

• Capability of a system to fulfil its mission, in
  a timely manner, in the presence of attacks,
  failures, or accidents

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System Survivability (continued)?
Table 11.1 Four key properties of a survivable
system
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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
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Backup and Recovery

• Backup and recovery policies are essential for
  most computing systems
• Many system managers use a layered backup
  schedule (full backup incremental backup)?
• 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

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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

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Security Breaches

• A gap in system security can be malicious or not
• Intrusions can be classified as
• Purely accidental
• Purposeful disruption of the systems operation
• Examples Hardware malfunctions, undetected
  errors in OS or applications
• Malicious or not, a breach of security severely
  damages the systems credibility

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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 non-synchronized processes access data
  records and modify some but not all of a records
  fields
• Buffer overrides most common cause for security
  breaches
• Network stack receiving a malformed packed
• Browser reading a malformed page

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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

Google Pack
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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

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Intentional Unauthorized Access (continued)?

• Wire Tapping Unauthorized users monitor or
  modify a users transmission
• Passive wire tapping (packet sniffing) 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
• Spoofing

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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. Example Athens Affair
  http//www.spectrum.ieee.org/jul07/5280
• Leaves the system vulnerable to future intrusion
• Trash collection Use of discarded materials such
  as disks, CDs, printouts, etc., to enter the
  system illegally

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Intentional Unauthorized Access (continued)?
Table 11.3 Average time required to guess
passwords up to ten alphabetic characters (A-Z)
using brute force
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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

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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

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Viruses (continued)?
Figure 11.2 A file infector virus attacks a
clean file (a) by attaching a small program to it
(b)?
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Viruses (continued)?
Table 11.4 Types of viruses
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Viruses (continued)?
Table 11.4 (continued) Types of viruses
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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
• Morris Worm 1988. Ten percent of the internet
  shut-down. Convicted to three years probation.
  Now professor at MIT.
• Trojan Horse A destructive program thats
  disguised as a legitimate or harmless program
• Allows the programs creator to secretly access
  users system

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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

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System Protection

• No single guaranteed method of protection
• Need for continuous attention to security issues
• System protection is multifaceted and protection
  methods include
• Use of antivirus software, firewalls, restrictive
  access and encryption

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Antivirus Software

• Software to combat viruses can be preventive,
  diagnostic, or both
• Preventive programs - checksums
• Diagnostic software looks for virus signatures
• 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

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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
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Antivirus Software (continued)?
Table 11.5 Websites containing current
information on systems security
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Firewalls

• A set of hardware and/or software designed to
  protect a networking system
• Sits between the Internet and network
• Mechanisms used by the firewall to perform
  various tasks include
• Packet filtering
• Proxy servers

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Firewalls (continued)?
Figure 11.5 Firewall sitting between campus
networks and Internet, filtering
requests for access
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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

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Firewalls (continued)?

• Packet filtering
• Firewall reviews header information for incoming
  and outgoing Internet packets. It drops packages
  based on source address, destination address, and
  port number
• Proxy server
• Hides important network information from
  outsiders by making network server invisible
• Proxy servers are invisible to users but are
  critical to the success of the firewall

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Authentication

• Authentication A verification that an individual
  trying to access a system is authorized to do so
• Kerberos A network authentication protocol
• Designed to provide strong authentication for
  client/server applications
• Uses strong cryptography
• Uses tickets to get access to resources. Tickets
  expire after a predetermined amount of time.

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Encryption

• Shared key cryptography
• Public key cryptography
• Disadvantages
• Increases systems overhead

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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
  other computer by changing the address recorded
  in packets it sends over the Internet

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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

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Password Construction (continued)?
Figure 11.8 Password verification flowchart
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Password Construction (continued)?
Table 11.6 Number of combinations of passwords
depending on their length and available character
set
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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

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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

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Password Alternatives

• something you have and something you know
• Use of a smart card Credit card like, but with
  better security.
• The smart card is read
• User then enters a secret code
• User is admitted to the system only if both the
  card and the secret code are validated

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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

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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
• Telephoning friends and co-workers to learn the
  names of users family members, pets, vacation
  destinations, favorite hobbies, car model, etc.

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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

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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
• Ethical lapses
• Illegally copy software
• Plagiarism
• Eavesdropping on e-mail, data, or voice
  communications
• Cracking programs (breaking program protection)?
• Virus writing

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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