Ch11- Security, Protection and Ethics Revised

8/3/2019 Ch11- Security, Protection and Ethics Revised

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Chapter 11

Security and Ethics


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Objectives

Understanding Operating Systems, Fourth

Edition2

You will be able to describe:

y The role of the operating system with regard to system security

y The effects of system security practices on overall systemperformance

y The levels of system security that can be implemented and thethreats posed by evolving technologies

y The differences between computer viruses and worms, and howthey spread

y The difficulties of teaching ethics to user groups and the role ofeducation in system security


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Role of the Operating System in Security


Edition3

y Operating system plays a key role in computer system security

y Any vulnerability at the operating system level opens the entire

system to attack

y The more complex and powerful the operating system, the morelikely it is to have vulnerabilities to attack

y System administrators must be on guard to arm their

operating systems with all available defenses against attack


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System Survivability


Edition4

y Capability of a system to fulfill its mission, in a timely

manner, in the presence of attacks, failures, or accidents

y Key properties of survivable systems:

y Resistance to attacks

y Recognition of attacks and resulting damage

y Recovery of essential services after an attack

y Adaptation and evolution of system defense mechanisms to

lessen future attacks


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System Survivability (continued)


Edition5

Table 11.1: Four key properties of a survivable system


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Levels ofProtection


Edition6

Table 11.2: A simplified comparison of security protection

required for three typical computer configurations

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


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Backup and Recovery


Edition7

y Backup and recovery policies are essential for most

computing systems

y Many system managers use a layered backup schedule

yBackups, with one set stored off-site, are crucial to disasterrecovery

y Written policies and procedures and regular user training are

essential elements of system management


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Backup and Recovery


Edition8

y Written security procedures should recommend:

y Frequent password changes

y Reliable backup procedures

y

Guidelines for loading new softwarey Compliance with software licenses

y Network safeguards

y Guidelines for monitoring network activity

y R

ules for terminal access


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Security Breaches


Edition9

y A gap in system security can be malicious or not

y Intrusions can be classified as:

y Due to uneducated users and unauthorized access to system

resourcesy Purposeful disruption of the systems operation

y Purely accidental

y Examples: Hardware malfunctions, undetected errors in OS or applications,

or natural disasters

y Malicious or not, a breach of security severely damages the

systems credibility


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Unintentional Intrusions


Edition10

y Any breach of security or modification of data that was not

the result of a planned intrusion

y Examples:

y

Accidental incomplete modification of datay When nonsynchronized processes access data records and modify some

but not all of a records fields

y Errors due to incorrect storage of data values

y e.g., When the field isnt large enough to hold the numeric value stored

there


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Unintentional Intrusions (continued)


Edition11

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


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Intentional Attacks


Edition12

y Types of Intentional attacks:

y Intentional unauthorized access

y e.g., denial of service attacks, browsing, wire tapping,

repeated trials, trap doors, and trash collection

y Viruses and worms

y Trojan Horses

y Bombs

y Blended threats


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IntentionalUnauthorized Access


Edition13

y Denial of service (DoS) attacks:

y Synchronized attempts to deny service to authorized users by

causing a computer to perform repeated unproductive task

y B

rowsing:y 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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(continued)


Edition14

y WireTapping: Unauthorized users monitor or modify ausers transmission

y Passive wire tapping: Refers to just listening to thetransmission but not changing the contents, and reasonsinclude:y To copy data while bypassing any authorization procedures

y To collect specific information such as password

y Active wire tapping: Data being sent is modifiedy Methods include between lines transmission and piggyback entry


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(continued)


Edition15

y RepeatedTrials:To enter systems by guessing authenticpasswords

y Trap doors: An unspecified and undocumented entry point

to the systemy Installed by a system diagnostician or programmer for future

use

y Leaves the system vulnerable to future intrusion

y Trash collection: Use of discarded materials such as disks,

CDs, printouts, etc., to enter the system illegally


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(continued)


Edition16

Table 11.3: Average time required to guess passwords up to

ten alphabetic characters (A-Z) using brute force


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(continued)


Edition17

y Malicious attacks on computers may violate state and federal law

under the Federal Computer Fraud andAbuseAct of 1986

y Those convicted have been sentenced to significant fines and jailterms, as well as confiscation of their computer equipment

y In the U.S., attempts to intrude into your system should be

reported to the FBI


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Viruses


Edition18

y Small programs written to alter the way a computer operates,

without permission of the user

y Must meet two criteria: It must be self-executing and self-

replicating

y Usually written to attack a certain operating system

y Spread via a wide variety of applications

y

Macro virus works by attaching itself to a template (such asNORMAL.DOT), which in turn is attached to word processing

documents


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Viruses (continued)


Edition19

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)


Edition20

Table 11.4: Types of viruses


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Viruses (continued)


Edition21

Table 11.4 (continued): Types of viruses


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Worms and Trojan Horses


Edition22

y Worm: A memory-resident program that copies itself from

one system to the next without requiring the aid of an

infected program file

y Results in slower processing time of real work

y Especially destructive on networks

y Trojan Horse: A destructive program thats disguised as a

legitimate or harmless program

y Allows the programs creator to secretly access users system


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Bombs and Blended Threats


Edition23

y Logic bomb: A destructive program with a fuse a certaintriggering event (such as a keystroke or connection with theInternet)

y Spreads unnoticed throughout a network

y Time bomb: A destructive program triggered by a specifictime, such as a day of the year

y BlendedThreat: Combines into one program thecharacteristics of other attacks

y

e.g., including a virus, worm, Trojan Horse, spyware, and othermalicious code into a single program


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Blended Threats (continued)


Edition24

BlendedThreats: (continued)

y Characteristics ofblended threat:

y Harms the affected system

y Spreads to other systems using multiple methods

y Attacks other systems from multiple points

y Propagates without human intervention

y Exploits vulnerabilities of target systems

y Protection: Combination of defenses in combination with

regular patch management


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System Protection


Edition25

y No single guaranteed method of protection

y System vulnerabilities include:

y File downloads, e-mail exchange

y Vulnerable firewallsy Improperly configured Internet connections, etc.

y Need for continuous attention to security issues

y System protection is multifaceted and protection methods

include:y Use of antivirus software, firewalls, restrictive access and

encryption


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Antivirus Software


Edition26

y Software to combat viruses can be preventive, diagnostic, or

both

y Preventive programs may calculate a checksum for each

production programy Diagnostic software compares file sizes, looks for replicating

instructions or unusual file activity

y Can sometimes remove the infection and leave the remainder

intacty Unable to repair worms, Trojan horses, or blended threats as

they are malicious code in entirety


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Antivirus Software (continued)


Edition27

Table 11.5: Websites containing current information on

systems security


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Antivirus Software (continued)


Edition28

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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Firewalls


Edition29

y A set of hardware and/or software designed to protect asystem by disguising its IP address from unauthorized users

y Sits between the Internet and network

y Blocks curious inquiries and potentially dangerous intrusionsfrom outside the system

y Mechanisms used by the firewall to perform various tasksinclude:

y Packet filtering

y Proxy servers


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Firewalls (continued)


Edition30

Figure 11.5: Firewall sitting between campus networks and

Internet, filtering requests for access


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Edition31

y Typical tasks of the firewall are to:

y Log activities that access the internet

y Maintain access control based on senders or receivers IP

addresses

y Maintain access control based on services that are requested

y Hide internal network from unauthorized users

y Verify that virus protection is installed and enforced

y Perform authentication based on the source of a request from theInternet


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Edition32

y Packet filtering:

y Firewall reviews header information for incoming and outgoingInternet packets to verify authenticity of source address,

destination address, and protocoly Proxy server:

y Hides important network information from outsiders by makingnetwork server invisible

y Determines if request for access to the network is valid

y Proxy servers are invisible to users but are critical to the success ofthe firewall


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Authentication


Edition33

y Authentication:A verification that an individual trying to

access a system is authorized to do so

y Kerberos: A network authentication protocol

y Need for password encryption to improve network security led to

development of Kerberos

y Designed to provide strong authentication for client/server

applications

y Uses strong cryptographyy Requires systematic revocation of access rights from clients who

no longer deserve to have access


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Authentication (continued)


Edition34

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


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Encryption


Edition35

y Most extreme protection method for sensitive data where datais put into a secret code

y To communicate with another system, data is encrypted,

transmitted, decrypted, and processedy Sender inserts public key with the message

y Message receiver required to have private key to decode themessage

y Disadvantages:y Increases systems overhead

y System becomes totally dependent on encryption process itself


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Sniffers and Spoofing


Edition36

y Sniffers: Programs that reside on computers attached to the

network

y Peruse data packets as they pass by, examine each one for

specific information

y e.g., Particularly problematic in wireless networks

y Spoofing: Assailant fakes IP addresses of an Internet server

by changing the address recorded in packets it sends over the

Internet

y Used when unauthorized users want to disguise themselves as

friendly sites


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Password Management


Edition37

y Most basic techniques used to protect hardware and softwareinvestments include:

y Good passwords

y Careful user training

y Password Construction:y Good password is unusual, memorable, and changed often

y Password files normally stored in encrypted form

y Password length has a direct effect on the ability of password to

survive password cracking attempts


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Password Construction (continued)


Edition38

Figure 11.8: Password verification flowchart


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Edition39

Table 11.6: Number of combinations of passwords

depending on their length and available character set


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Edition40

y Reliable techniques for generating a good password:

y Use minimum of eight characters, including numbers and

nonalphanumeric characters

y Create a misspelled word or join bits of phrases into a word thatseasy to remember

y Follow a certain pattern on the keyboard

y Create acronyms from memorable sentences

y Use upper and lowercase characters if allowedy Never use a word thats included in any dictionary


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Edition41

y Dictionary attack: A method of breaking encrypted

passwords

y Requirements:

y A copy of the encrypted password file

y Algorithm used to encrypt the passwords

y Prevention:

y Some operating systems salt user passwords with extra random bits to make

them less vulnerable to dictionary attacks


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Password Alternatives


Edition42

y Use of a smart card

y A credit card-sized calculator that requires both something youhave and something you know

y

Displays a constantly changing multidigit number synchronizedwith an identical number generator in the system

y User must type in the number that appears at that moment on thesmart card

y For added protection, user then enters a secret code

y User is admitted to the system only if both number and code arevalidated


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Password Alternatives (continued)


Edition43

y Biometrics:

y The science and technology of identifying individuals based on

unique biological characteristics of each person

y Current research focuses ony Analysis of the human face, fingerprints, hand measurements, iris/retina, and

voice prints

y Positively identifies the person being scanned

y C

ritical factor is reducing the margin of errory Presently, biometric authentication is expensive


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Social Engineering


Edition44

y A technique whereby system intruders gain access to

information about a legitimate user to learn active passwords by

y Looking in and around the users desk for a written reminder

y Trying the user logon ID as the password

y Searching logon scripts

y 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)


Edition45

y Phishing: Intruder pretends to be a legitimate entity andcontacts unwary users asking them to reconfirm theirpersonal and/or financial information

y Example: 2003 incident involving eBay customers

y Default passwords:y Pose unique vulnerabilities because they are widely known

y Routinely shipped with hardware or software

y Routinely passed from one hacker to the next

y

Should be changed immediately


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Ethics


Edition46

y Ethical behavior: Be good. Do good.

y IEEE and ACM issued a standard of ethics in 1992

y Apparent lack of ethics in computing is a significant departure

from other professionsy Consequences of ethical lapses:

y Illegally copied software can result in lawsuits and fines

y Plagiarism is illegal and punishable by law

y Eavesdropping on e-mail, data, or voice communications issometimes illegal and usually unwarranted


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Ethics (continued)


Edition47

y Consequences of ethical lapses: (continued)

y Cracking (malicious hacking) causes systems owner and users to

question the validity of systems data

y U

nethical use of technology is clearly the wrong thing to doy Specific activities to teach ethics can include:

y Publish policies that clearly state which actions will and will not be

condoned

y

Teach a regular seminar on the subject including real-life casehistories

y Conduct open discussions of ethical questions


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Summary


Edition48

y Cant overemphasize the importance of keeping the systemsecure

y System is only as good as the integrity of the data thats stored

on ity A single breach of security whether catastrophic or not,

whether accidental or not damages the systems integrity

y Damaged integrity threatens the viability of the best-designed

system, its managers, its designers, and its usersy Vigilant security precautions are essential

Documents

Ch11- Security, Protection and Ethics Revised