Guide to Operating
System Security
Chapter 1
Operating Systems Security
– Keeping Computers and
Networks Secure
Objectives
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Explain what operating system and network
security means
Discuss why security is necessary
Explain the cost factors related to security
Describe the types of attacks on operating
systems and networks
Discuss system hardening, including features
in operating systems and networks that enable
hardening
Guide to Operating System Security
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What Is Operating System and
Network Security?

Ability to reliably store, modify, protect, and
grant access to information, so that
information is only available to designated
users
Guide to Operating System Security
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Operating Systems and Security

Operating systems
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Provide basic programming instructions to
computer hardware
Interface with user application software and
computer’s BIOS to allow applications to interact
with hardware
Security issue

Potential to provide security functions at every
level of operation
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Operating System Components
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Application programming interface (API)
Basic input/output system (BIOS)
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Basic form of security: Configure BIOS password
security
Kernel
Resource managers
Device drivers
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Operating System Functions and
Components
Guide to Operating System Security
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Computer Networks and
Security

Computer network

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System of computers, print devices, network
devices, and computer software linked by
communications cabling or radio and microwaves
Security issue

All networks have vulnerable points that require
security
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Types of Networks

Classified by reach and complexity
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Local area networks (LANs)
Metropolitan area networks (MANs)
Wide area networks (WANs)
Enterprise networks
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Resources in an Enterprise
Network
Guide to Operating System Security
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Careers in Information Security

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Number of jobs has increased by 100% per
year since 1998
Potential for healthy salaries and
organizational advancement
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Why Security Is Necessary
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Protects information and resources
Ensures privacy
Facilitates workflow
Addresses security holes and software bugs
Compensates for human error or neglect
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Protecting Information and
Resources

Security protects information and resources of:

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Businesses
Educational institutions
Government
Telecommuters
Personal users
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Ensuring Privacy

Potential for serious legal and business
consequences when an intruder accesses
private information
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Facilitating Workflow

Potential for loss of money, data, or both if a
step in the work process is compromised due
to a security problem
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Addressing Security Holes or
Software Bugs

After purchasing a new OS, software, or
hardware:
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Test rigorously for security and reliability
Check security defaults
Install patches immediately
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Compensating for
Human Error or Neglect
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Use an OS that enables the organization to set
up security policies
Develop written security policies
Implement training
Test security of new operating systems and
software
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Setting Up Local Security
Policies
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Cost Factors

Cost of deploying security

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Should be an element in total cost of ownership
(TCO)
Cost of not deploying security
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Types of Attacks
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Standalone
workstation or server
attacks
Attacks enabled by
access to passwords
Viruses, worms, and
Trojan horses
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Guide to Operating System Security
Buffer attacks
Denial of service
Source routing attack
Spoofing
E-mail attack
Port scanning
Wireless attacks
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Standalone Workstation
or Server Attacks
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Easy to take advantage of a logged-on
computer that is unattended and unprotected
Avoid by setting up a password-protected
screen saver
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Attacks Enabled by Access to
Passwords
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Users defeat password protection by
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Sharing them with others
Writing them down and displaying them
Attackers have sophisticated ways of gaining
password access
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Attempting to Log On to a Telnet
Account
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Viruses
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Virus
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Able to replicate throughout a system
Infects a disk/file, which infects other disks/files
Some cause damage; some don’t
Virus hoax

E-mail falsely warning of a virus
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Worm
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Endlessly replicates on the same computer, or
sends itself to many other computers on a
network
Continues to create new files but does not
infect existing files
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Trojan Horse
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Appears useful and harmless, but does harm
Can provide hacker with access to or control of
the computer
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Buffer Attacks
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Attacker tricks buffer software into attempting
to store more information than it can contain
(buffer overflow)
The extra information can be malicious
software
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Denial of Service (DoS) Attacks

Interfere with normal access to network host,
Web site, or service by flooding network with:
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Useless information, or
Frames or packets containing errors that are not
identified by a network service
Distributed DoS attack

One computer causes others to launch attacks
directed at one or more targets
Guide to Operating System Security
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Source Routing Attack
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
Attacker modifies source address and routing
information to make a packet appear to come
from a different source
Can be used to breach a privately configured
network
A form of spoofing
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Spoofing
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Address of source computer is changed to
make a packet appear to come from a different
computer
Can be used to initiate access to a computer
Can appear as just another transmission to a
computer from a legitimate source
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E-mail Attack
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Attached file may contain:

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Virus, worm, or Trojan horse
Macro that contains malicious code
E-mail may contain Web link to a rogue Web
site
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Port Scanning
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Attacker determines live IP address, then runs
port scanning software (eg Nmap or Strobe) to
find a system on which a key port is open or
not in use
To block access through open ports:
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Stop OS services or processes that are not in use
Configure a service only to start manually with
your knowledge
Unload unnecessary NLMs
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Sample TCP Ports
Guide to Operating System Security
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Using the kill Command
in Red Hat Linux
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Managing Mac OS X Sharing
Services
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Wireless Attacks
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Generally involve scanning multiple channels
Key elements
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Wireless network interface card
Omnidirectional antenna
War-driving software
Difficult to determine when someone has
compromised a wireless network
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Organizations That Help
Prevent Attacks (Continued)
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American Society for Industrial Security
(ASIS)
Computer Emergency Response Team
Coordination Center (CERT/CC)
Forum of Incident Response and Security
Teams (FIRST)
InfraGard
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Organizations That Help
Prevent Attacks (Continued)
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Information Security Forum (ISF)
Information Systems Security Association
(ISSA)
National Security Institute (NSI)
SysAdmin, Audit, Network, Security (SANS)
Institute
Guide to Operating System Security
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Hardening Your System

Taking specific actions to block or prevent
attacks by means of operating system and
network security methods
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General Steps to Harden a
System (Continued)
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Learn about OS and network security features
Consult Web sites of security organizations
Only deploy services and processes that are
absolutely necessary
Deploy dedicated servers, firewalls, and
routers
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General Steps to Harden a
System (Continued)
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Use OS features that are provided for security
Deploy as many obstructions as possible
Audit security regularly
Train users to be security conscious
Monitor OSs and networks regularly for
attackers
Guide to Operating System Security
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Overview of Operating System
Security Features
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Logon security
Digital certificate
security
File and folder
security
Shared resource
security
Guide to Operating System Security
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Security policies
Remote access
security
Wireless security
Disaster recovery
41
Logon Security
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Requires user account and password to access
OS or network
User account provides access to the domain
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Objects in a Domain
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Digital Certificate Security

Verifies authenticity of the communication to
ensure that communicating parties are who
they say they are
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File and Folder Security
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Lists of users and user groups can be given
permission to access resources
Attributes can be associated with resources to
manage access and support creation of
backups
Guide to Operating System Security
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Shared Resource Security
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Ways to control access to resources:
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Use a list of users and groups that should be
configured
Use domains
Publish resources in a directory service (eg, Active
Directory or NDS)
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Using an Access List
Guide to Operating System Security
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Security Policies
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Security default settings that apply to a
resource offered through an OS or directory
service
May apply only to local computer, or to other
computers
May specify that user account passwords must
be a minimum length and be changed at
regular intervals
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Remote Access Security
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Enable remote access only when absolutely
necessary
Many forms, including:

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Callback security
Data encryption
Access authentication
Password security
Guide to Operating System Security
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Wireless Security
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Implement Wired Equivalent Privacy (WEP)
Create a list of authorized wireless users based
on the permanent address assigned to the
wireless interface in the computer
Guide to Operating System Security
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Disaster Recovery

Use of hardware and software techniques to
prevent loss of data

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Perform backups
Store backups in a second location
Use redundant hard disks
Enables restoration of systems and data
without loss of critical information
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Overview of Network Security
Features

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Authentication and encryption
Firewalls
Topology
Monitoring
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Authentication

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Using a method to validate users who attempt
to access a network or resources, to ensure
they are authorized
Examples

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User accounts with passwords
Smart cards
Biometrics
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Encryption


Protects information sent over a network by
making it appear unintelligible
Generally involves using a mathematical key
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Firewalls

Software or hardware placed between
networks that selectively allows or denies
access
Guide to Operating System Security
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Topology


Different designs yield different results in
terms of security planning and hardening
Also affects security in terms of where specific
devices are placed
Guide to Operating System Security
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Monitoring


Involves determining performance and use of
an OS or network
Enables you to determine weak points of a
system or network and address them before a
problem occurs
Guide to Operating System Security
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Summary

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Operating system and network security
Why such security is vital
Careers in information security
The cost of security; the cost of not having security
Common types of attacks
Techniques for guarding against attacks on operating
systems and on networks
Guide to Operating System Security
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