CIT 016 Review for Final

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CIT 016Review for Final

• Security Guide to Network Security Fundamentals
• Second Edition

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Defining Information Security

• Three characteristics of information must be
  protected by information security
• Confidentiality
• Integrity
• Availability
• Information security achieved through a
  combination of three entities

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Importance of Information Security

• Information security is important to businesses
• Prevents data theft
• Avoids legal consequences of not securing
  information
• Maintains productivity
• Foils cyberterrorism
• Thwarts identity theft

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Preventing Data Theft

• Theft of data is single largest cause of
  financial loss due to a security breach
• One of the most important objectives of
  information security is to protect important
  business and personal data from theft

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Developing Attacker Profiles

• Six categories
• Hackers
• Crackers
• Script kiddies
• Spies
• Employees
• Cyberterrorists

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Developing Attacker Profiles
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Hackers

• Person who uses advanced computer skills to
  attack computers, but not with a malicious intent
• Use their skills to expose security flaws
• Know that breaking in to a system is illegal but
  do not intend on committing a crime
• Hacker code of ethics
• Target should have had better security

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Crackers

• Person who violates system security with
  malicious intent
• Have advanced knowledge of computers and networks
  and the skills to exploit them
• Destroy data, deny legitimate users of service,
  or otherwise cause serious problems on computers
  and networks

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Script Kiddies

• Break into computers to create damage
• Not as skilled as Crackers
• Download automated hacking software from Web
  sites and use it to break into computers
• Tend to be young computer users with large
  amounts of leisure time, which they can use to
  attack systems

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Spies

• Person hired to break into a computer and steal
  information
• Do not randomly search for unsecured computers to
  attack
• Hired to attack a specific computer that contains
  sensitive information
• Possess excellent computer skills
• Could also use social engineering to gain access
  to a system
• Financially motivated

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Employees

• One of the largest information security threats
  to business
• Employees break into their companys computer for
  these reasons
• To show the company a weakness in their security
• Being overlooked, revenge
• For money
• Inside of network is often vulnerable because
  security focus is at the perimeter
• Unskilled user could inadvertently launch virus,
  worm or spyware

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Cyberterrorists

• Experts fear terrorists will attack the network
  and computer infrastructure to cause panic
• Cyberterrorists motivation may be defined as
  ideology, or attacking for the sake of their
  principles or beliefs
• Targets that are high on the cyberterrorists list
  are
• Infrastructure outages
• Internet itself

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Cyberterrorists (continued)

• Three goals of a cyberattack
• Deface electronic information to spread
  disinformation and propaganda
• Deny service to legitimate computer users
• Commit unauthorized intrusions into systems and
  networks that result in critical infrastructure
  outages and corruption of vital data

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Understanding Security Principles

• Ways information can be attacked
• Crackers can launch distributed denial-of-service
  (DDoS) attacks through the Internet
• Spies can use social engineering
• Employees can guess other users passwords
• Hackers can create back doors
• Protecting against the wide range of attacks
  calls for a wide range of defense mechanisms

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Layering

• Layered security approach has the advantage of
  creating a barrier of multiple defenses that can
  be coordinated to thwart a variety of attacks
• Information security likewise must be created in
  layers
• All the security layers must be properly
  coordinated to be effective

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Layering (continued)
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Limiting

• Limiting access to information reduces the threat
  against it
• Only those who must use data should have access
  to it
• Access must be limited for a subject (a person or
  a computer program running on a system) to
  interact with an object (a computer or a database
  stored on a server)
• The amount of access granted to someone should be
  limited to what that person needs to know or do

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Limiting (continued)
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Diversity

• Diversity is closely related to layering
• You should protect data with diverse layers of
  security, so if attackers penetrate one layer,
  they cannot use the same techniques to break
  through all other layers
• Using diverse layers of defense means that
  breaching one security layer does not compromise
  the whole system
• Not just perimeter security
• Possibly using different vendors
• Increased administrative overhead

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Diversity (continued)

• You can set a firewall to filter a specific type
  of traffic, such as all inbound traffic, and a
  second firewall on the same system to filter
  another traffic type, such as outbound traffic
• Use application layer filtering by a Linux box
  before traffic hits the firewall
• Use one device as the firewall and different
  device as the spam filter
• Using firewalls produced by different vendors
  creates even greater diversity
• This could add some complexity

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Obscurity

• Obscuring what goes on inside a system or
  organization and avoiding clear patterns of
  behavior make attacks from the outside difficult
• Network Address Translation
• Port Address Translation
• Internal ports different from external
• External port 80 ? Internal port 8080

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Simplicity

• Complex security systems can be difficult to
  understand, troubleshoot, and feel secure about
• The challenge is to make the system simple from
  the inside but complex from the outside

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Using Effective Authentication Methods

• Information security rests on three key pillars
• Authentication
• Access control (Authorization)
• Auditing (Accounting)
• Also Known as AAA

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Effective Authentication Methods

• Authentication
• Process of providing identity
• Can be classified into three main categories
  what you know, what you have, what you are
• Most common method providing a user with a
  unique username and a secret password

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Username and Password

• ID management
• Users single authenticated ID is shared across
  multiple networks or online businesses
• Attempts to address the problem of users having
  individual usernames and passwords for each
  account (thus, resorting to simple passwords that
  are easy to remember)
• Can be for users and for computers that share
  data

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Disabling Nonessential Systems

• First step in establishing a defense against
  computer attacks is to turn off all nonessential
  services
• Disabling services that are not necessary
  restricts attackers can use
• Reducing the attack surface

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Disabling Nonessential Systems

• A service can be set to one of the following
  modes
• Automatic
• Manual
• Disabled
• Besides preventing attackers from attaching
  malicious code to services, disabling
  nonessential services blocks entries into the
  system

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Hardening Operating Systems

• Hardening process of reducing vulnerabilities
• A hardened system is configured and updated to
  protect against attacks
• Three broad categories of items should be
  hardened
• Operating systems
• Applications that the operating system runs
• Networks

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Hardening Operating Systems

• You can harden the operating system that runs on
  the local client or the network operating system
  (NOS) that manages and controls the network, such
  as Windows Server 2003 or Novell NetWare

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Applying Updates

• Operating systems are intended to be dynamic
• As users needs change, new hardware is
  introduced, and more sophisticated attacks are
  unleashed, operating systems must be updated on a
  regular basis
• However, vendors release a new version of an
  operating system every two to four years
• Vendors use certain terms to refer to the
  different types of updates.

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Applying Updates (continued)

• A service pack (a cumulative set of updates
  including fixes for problems that have not been
  made available through updates) provides the
  broadest and most complete update
• A hotfix does not typically address security
  issues instead, it corrects a specific software
  problem

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Applying Updates (continued)
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Applying Updates (continued)

• A patch or a software update fixes a security
  flaw or other problem
• May be released on a regular or irregular basis,
  depending on the vendor or support team
• A good patch management system
• Design patches to update groups of computers
• Include reporting system
• Download patches from the Internet
• Distribute patches to other computers

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Securing the File System

• Another means of hardening an operating system is
  to restrict user access
• Generally, users can be assigned permissions to
  access folders (also called directories in DOS
  and UNIX/Linux) and the files contained within
  them

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Firmware Updates

• RAM is volatile?interrupting the power source
  causes RAM to lose its entire contents
• Read-only memory (ROM) is different from RAM in
  two ways
• Contents of ROM are fixed
• ROM is nonvolatile?disabling the power source
  does not erase its contents

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Firmware Updates (continued)

• ROM, Erasable Programmable Read-Only Memory
  (EPROM), and Electrically Erasable Programmable
  Read-Only Memory (EEPROM) are firmware (flash)
• To erase an EPROM chip, hold the chip under
  ultraviolet light so the light passes through its
  crystal window
• The contents of EEPROM chips can also be erased
  using electrical signals applied to specific pins

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Firmware Updates (continued)

• To update a network device we copy over a new
  version of the OS software to the flash memory of
  the device.
• This can be done via a tftp server or a compact
  flash reader/writer
• Router copy tftp flash
• Having the firmware updated ensures the device is
  not vulnerable to bugs in the OS that can be
  exploited

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Network Configuration

• You must properly configure network equipment to
  resist attacks
• The primary method of resisting attacks is to
  filter data packets as they arrive at the
  perimeter of the network
• In addition to making sure the perimeter is
  secure, make sure the device itself is secure by
  using strong passwords and encrypted connections
• SSH instead of Telnet and console, vty passwords

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Configuring Packet Filtering

• The User Datagram Protocol (UDP) provides for a
  connectionless TCP/IP transfer
• TCP and UDP are based on port numbers
• Socket combination of an IP address and a port
  number
• The IP address is separated from the port number
  by a colon, as in 198.146.118.2080

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Network Configuration

• Rule base or access control list (ACL) rules a
  network device uses to permit or deny a packet
  (not to be confused with ACLs used in securing a
  file system)
• Rules are composed of several settings (listed on
  pages 122 and 123 of the text)
• Observe the basic guidelines on page 124 of the
  text when creating rules

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Network Cable Plant

• Cable plant physical infrastructure of a network
  (wire, connectors, and cables) used to carry data
  communication signals between equipment
• Three types of transmission media
• Coaxial cables
• Twisted-pair cables
• Fiber-optic cables

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Twisted-Pair Cables

• Standard for copper cabling used in computer
  networks today, replacing thin coaxial cable
• Composed of two insulated copper wires twisted
  around each other and bundled together with other
  pairs in a jacket

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Twisted-Pair Cables (continued)

• Shielded twisted-pair (STP) cables have a foil
  shielding on the inside of the jacket to reduce
  interference
• Unshielded twisted-pair (UTP) cables do not have
  any shielding
• Twisted-pair cables have RJ-45 connectors

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Fiber-Optic Cables

• Coaxial and twisted-pair cables have copper wire
  at the center that conducts an electrical signal
• Fiber-optic cable uses a very thin cylinder of
  glass (core) at its center instead of copper that
  transmit light impulses
• A glass tube (cladding) surrounds the core
• The core and cladding are protected by a jacket

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Hardening Standard Network Devices

• A standard network device is a typical piece of
  equipment that is found on almost every network,
  such as a workstation, server, switch, or router
• This equipment has basic security features that
  you can use to harden the devices

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Switches and Routers

• Switch
• Most commonly used in Ethernet LANs
• Receives a packet from one network device and
  sends it to the destination device only
• Limits the collision domain (part of network on
  which multiple devices may attempt to send
  packets simultaneously)
• A switch is used within a single network
• Routers connect two or more single networks to
  form a larger network

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Hardening Network Security Devices

• The final category of network devices includes
  those designed and used strictly to protect the
  network
• Include
• Firewalls
• Intrusion-detection systems
• Network monitoring and diagnostic devices

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Firewalls

• Typically used to filter packets
• Designed to prevent malicious packets from
  entering the network or its computers (sometimes
  called a packet filter)
• Typically located outside the network security
  perimeter as first line of defense
• Can be software or hardware configurations

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Firewalls (continued)

• Software firewall runs as a program on a local
  computer (sometimes known as a personal firewall)
• Enterprise firewalls are software firewalls
  designed to run on a dedicated device and protect
  a network instead of only one computer
• One disadvantage is that it is only as strong as
  the operating system of the computer

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Firewalls (continued)

• Filter packets in one of two ways
• Stateless packet filtering permits or denies
  each packet based strictly on the rule base
• Stateful packet filtering records state of a
  connection between an internal computer and an
  external server makes decisions based on
  connection and rule base
• Can perform content filtering to block access to
  undesirable Web sites

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Designing Network Topologies

• Topology physical layout of the network devices,
  how they are interconnected, and how they
  communicate
• Essential to establishing its security
• Although network topologies can be modified for
  security reasons, the network still must reflect
  the needs of the organization and users

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Security Zones

• One of the keys to mapping the topology of a
  network is to separate secure users from
  outsiders through
• Demilitarized Zones (DMZs)
• Intranets
• Extranets

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Demilitarized Zones (DMZs)

• Separate networks that sit outside the secure
  network perimeter
• Outside users can access the DMZ, but cannot
  enter the secure network
• For extra security, some networks use a DMZ with
  two firewalls
• The types of servers that should be located in
  the DMZ include
• Web servers E-mail servers
• Remote access servers FTP servers

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Network Address Translation (NAT)

• You cannot attack what you do not see is the
  philosophy behind Network Address Translation
  (NAT) systems
• Hides the IP addresses of network devices from
  attackers
• Computers are assigned special IP addresses
  (known as private addresses)

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Network Address Translation (NAT)

• These IP addresses are not assigned to any
  specific user or organization anyone can use
  them on their own private internal network
• Port address translation (PAT) is a variation of
  NAT
• Each packet is given the same IP address, but a
  different TCP port number

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Virtual LANs (VLANs)

• Segment a network with switches to divide the
  network into a hierarchy
• Core switches reside at the top of the hierarchy
  and carry traffic between switches
• Workgroup switches are connected directly to the
  devices on the network
• Core switches must work faster than workgroup
  switches because core switches must handle the
  traffic of several workgroup switches

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Virtual LANs (VLANs)
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Virtual LANs (VLANs)

• Segment a network by grouping similar users
  together
• Instead of segmenting by user, you can segment a
  network by separating devices into logical groups
  (known as creating a VLAN)

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Secure/MIME (S/MIME)

• Protocol that adds digital signatures and
  encryption to Multipurpose Internet Mail
  Extension (MIME) messages
• Provides these features
• Digital signatures Interoperability
• Message privacy Seamless integration
• Tamper detection

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Pretty Good Privacy (PGP)

• Functions much like S/MIME by encrypting messages
  using digital signatures
• A user can sign an e-mail message without
  encrypting it, verifying the sender but not
  preventing anyone from seeing the contents
• First compresses the message
• Reduces patterns and enhances resistance to
  cryptanalysis
• Creates a session key (a one-time-only secret
  key)
• This key is a number generated from random
  movements of the mouse and keystrokes typed

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Pretty Good Privacy (PGP)

• Uses a passphrase to encrypt the private key on
  the local computer
• Passphrase
• A longer and more secure version of a password
• Typically composed of multiple words
• More secure against dictionary attacks

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Pretty Good Privacy (PGP)
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Securing Web Communications

• Most common secure connection uses the Secure
  Sockets Layer/Transport Layer Security protocol
• One implementation is the Hypertext Transport
  Protocol over Secure Sockets Layer

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Secure Sockets Layer (SSL)/Transport Layer
Security (TLS)

• SSL protocol developed by Netscape to securely
  transmit documents over the Internet
• Uses private key to encrypt data transferred over
  the SSL connection
• Version 20 is most widely supported version
• Personal Communications Technology (PCT),
  developed by Microsoft, is similar to SSL

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Secure Sockets Layer (SSL)/Transport Layer
Security (TLS)

• TLS protocol guarantees privacy and data
  integrity between applications communicating over
  the Internet
• An extension of SSL they are often referred to
  as SSL/TLS
• SSL/TLS protocol is made up of two layers

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Secure Sockets Layer (SSL)/Transport Layer
Security (TLS)

• TLS Handshake Protocol allows authentication
  between server and client and negotiation of an
  encryption algorithm and cryptographic keys
  before any data is transmitted
• FORTEZZA is a US government security standard
  that satisfies the Defense Messaging System
  security architecture
• Has cryptographic mechanism that provides message
  confidentiality, integrity, authentication, and
  access control to messages, components, and even
  systems

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Secure Hypertext Transport Protocol (HTTPS)

• One common use of SSL is to secure Web HTTP
  communication between a browser and a Web server
• This version is plain HTTP sent over SSL/TLS
  and named Hypertext Transport Protocol over SSL
• Sometimes designated HTTPS, which is the
  extension to the HTTP protocol that supports it
• Whereas SSL/TLS creates a secure connection
  between a client and a server over which any
  amount of data can be sent security, HTTPS is
  designed to transmit individual messages securely

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Tunneling Protocols

• Tunneling technique of encapsulating one packet
  of data within another type to create a secure
  link of transportation

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IEEE 8021x

• Based on a standard established by the Institute
  for Electrical and Electronic Engineers (IEEE)
• Gaining wide-spread popularity
• Provides an authentication framework for
  802-based LANs (Ethernet, Token Ring, wireless
  LANs)
• Uses port-based authentication mechanisms
• Switch denies access to anyone other than an
  authorized user attempting to connect to the
  network through that port

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IEEE 8021x (continued)

• Network supporting the 8021x protocol consists of
  three elements
• Supplicant client device, such as a desktop
  computer or personal digital assistant (PDA),
  which requires secure network access
• Authenticator serves as an intermediary device
  between supplicant and authentication server
• Authentication server receives request from
  supplicant through authenticator

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802.1x

• 802.1x is a standardized framework defined by the
  IEEE that is designed to provide port-based
  network access.
• The 802.1x framework defines three roles in the
  authentication process
• Supplicant endpoint that needs network access
• Authenticator switch or access point
• Authentication Server RADIUS, TACACS, LDAP
• The authentication process consists of exchanges
  of Extensible Authentication Protocol (EAP)
  messages between the supplicant and the
  authentication server.

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802.1x Roles

• Microsoft Windows XP includes 802.1x supplicant
  support

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Remote Authentication Dial-In User Service
(RADIUS)

• Originally defined to enable centralized
  authentication and access control and PPP
  sessions
• Requests are forwarded to a single RADIUS server
• Supports authentication, authorization, and
  auditing functions
• After connection is made, RADIUS server adds an
  accounting record to its log and acknowledges the
  request
• Allows company to maintain user profiles in a
  central database that all remote servers can share

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Terminal Access Control Access Control System
(TACACS)

• Industry standard protocol specification that
  forwards username and password information to a
  centralized server (TACACS)
• Whereas communication between a NAS and a TACACS
  server is encrypted, communication between a
  client and a NAS is not
• TACACS utilizes TCP port 49.
• It is a Cisco proprietary enhancement to original
  TACACS protocol.

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IP Security (IPSec) (continued)

• IPSec is a set of protocols developed to support
  the secure exchange of packets
• Considered to be a transparent security protocol
• Transparent to applications, users, and software
• Provides three areas of protection that
  correspond to three IPSec protocols
• Authentication
• Confidentiality
• Key management

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IP Security (IPSec) (continued)
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IP Security (IPSec) (continued)

• Supports two encryption modes
• Transport mode encrypts only the data portion
  (payload) of each packet, yet leaves the header
  encrypted
• Tunnel mode encrypts both the header and the data
  portion
• IPSec accomplishes transport and tunnel modes by
  adding new headers to the IP packet
• The entire original packet is then treated as the
  data portion of the new packet

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IP Security (IPSec) (continued)
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IP Security (IPSec) (continued)

• Both Authentication Header (AH) and Encapsulating
  Security Payload (ESP) can be used with Transport
  or Tunnel mode, creating four possible transport
  mechanisms
• AH in transport mode
• AH in tunnel mode
• ESP in transport mode
• ESP in tunnel mode

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Virtual Private Networks (VPNs)

• Takes advantage of using the public Internet as
  if it were a private network
• Allow the public Internet to be used privately
• Prior to VPNs, organizations were forced to lease
  expensive data connections from private carriers
  so employees could remotely connect to the
  organizations network

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Virtual Private Networks (VPNs)

• Two common types of VPNs include
• Remote-access VPN or virtual private dial-up
  network (VPDN) user-to-LAN connection used by
  remote users
• Site-to-site VPN multiple sites can connect to
  other sites over the Internet
• VPN transmissions achieved through communicating
  with endpoints
• An endpoint can be software on a local computer,
  a dedicated hardware device such as a VPN
  concentrator, or even a firewall

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Basic WLAN Security

• Two areas
• Basic WLAN security
• Enterprise WLAN security
• Basic WLAN security uses two new wireless tools
  and one tool from the wired world
• Service Set Identifier (SSID) beaconing
• MAC address filtering
• Wired Equivalent Privacy (WEP)

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Service Set Identifier (SSID) Beaconing

• A service set is a technical term used to
  describe a WLAN network
• Three types of service sets
• Independent Basic Service Set (IBSS)
• Basic Service Set (BSS)
• Extended Service Set (ESS)
• Each WLAN is given a unique SSID

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MAC Address Filtering

• Another way to harden a WLAN is to filter MAC
  addresses
• The MAC address of approved wireless devices is
  entered on the AP
• A MAC address can be spoofed
• When wireless device and AP first exchange
  packets, the MAC address of the wireless device
  is sent in plaintext, allowing an attacker with a
  sniffer to see the MAC address of an approved
  device

85
Wired Equivalent Privacy (WEP)

• Optional configuration for WLANs that encrypts
  packets during transmission to prevent attackers
  from viewing their contents
• Uses shared keys?the same key for encryption and
  decryption must be installed on the AP, as well
  as each wireless device
• A serious vulnerability in WEP is that the IV is
  not properly implemented
• Every time a packet is encrypted it should be
  given a unique IV

86
Other Wireless Authentication Protocols

• Wi-Fi Protected Access WPA
• The TKIP encryption algorithm was developed for
  WPA to provide improvements to WEP
• WPA2
• WiFi Alliance branded version of the final
  802.11i standard
• WPA2 support EAP authentication methods using
  RADIUS servers and preshared key (PSK) based
  security
• 802.1X
• LEAP
• PEAP
• TKIP

87
Untrusted Network

• The basic WLAN security of SSID beaconing, MAC
  address filtering, and WEP encryption is not
  secure enough for an organization to use
• One approach to securing a WLAN is to treat it as
  an untrusted and unsecure network
• Requires that the WLAN be placed outside the
  secure perimeter of the trusted network

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Untrusted Network (continued)
89
Trusted Network (continued)

• WPA encryption addresses the weaknesses of WEP by
  using the Temporal Key Integrity Protocol (TKIP)
• TKIP mixes keys on a per-packet basis to improve
  security
• Although WPA provides enhanced security, the IEEE
  80211i solution is even more secure
• 80211i is expected to be released sometime in
  2004

90
Cryptography Terminology

• Cryptography science of transforming information
  so it is secure while being transmitted or stored
• Steganography attempts to hide existence of data
• Encryption changing the original text to a
  secret message using cryptography

91
Cryptography Terminology

• Decryption reverse process of encryption
• Algorithm process of encrypting and decrypting
  information based on a mathematical procedure
• Key value used by an algorithm to encrypt or
  decrypt a message

92
Cryptography Terminology

• Weak key mathematical key that creates a
  detectable pattern or structure
• Plaintext original unencrypted information (also
  known as clear text)
• Cipher encryption or decryption algorithm tool
  used to create encrypted or decrypted text
• Ciphertext data that has been encrypted by an
  encryption algorithm

93
Cryptography Terminology (continued)
94
Defining Hashing

• Hashing, also called a one-way hash, creates a
  ciphertext from plaintext
• Cryptographic hashing follows this same basic
  approach
• Hash algorithms verify the accuracy of a value
  without transmitting the value itself and
  subjecting it to attacks
• A practical use of a hash algorithm is with
  automatic teller machine (ATM) cards

95
Defining Hashing (continued)

• Hashing is typically used in two ways
• To determine whether a password a user enters is
  correct without transmitting the password itself
• To determine the integrity of a message or
  contents of a file
• Hash algorithms are considered very secure if the
  hash that is produced has the characteristics
  listed on pages 276 and 277 of the text

96
Message Digest (MD)

• Message digest 2 (MD2) takes plaintext of any
  length and creates a hash 128 bits long
• MD2 divides the message into 128-bit sections
• If the message is less than 128 bits, data known
  as padding is added
• Message digest 4 (MD4) was developed in 1990 for
  computers that processed 32 bits at a time
• Takes plaintext and creates a hash of 128 bits
• The plaintext message itself is padded to a
  length of 512 bits

97
Message Digest (MD)

• Message digest 5 (MD5) is a revision of MD4
  designed to address its weaknesses
• The length of a message is padded to 512 bits
• The hash algorithm then uses four variables of 32
  bits each in a round-robin fashion to create a
  value that is compressed to generate the hash

98
Secure Hash Algorithm (SHA)

• Patterned after MD4 but creates a hash that is
  160 bits in length instead of 128 bits
• The longer hash makes it more resistant to
  attacks
• SHA pads messages less than 512 bits with zeros
  and an integer that describes the original length
  of the message

99
Protecting with Symmetric Encryption Algorithms

• A block cipher manipulates an entire block of
  plaintext at one time
• The plaintext message is divided into separate
  blocks of 8 to 16 bytes and then each block is
  encrypted independently
• The blocks can be randomized for additional
  security

100
Data Encryption Standard (DES)

• One of the most popular symmetric cryptography
  algorithms
• DES is a block cipher and encrypts data in 64-bit
  blocks
• The 8-bit parity bit is ignored so the effective
  key length is only 56 bits
• DES encrypts 64-bit plaintext by executing the
  algorithm 16 times
• The four modes of DES encryption are summarized
  on pages 282 and 283

101
Triple Data Encryption Standard (3DES)

• Uses three rounds of encryption instead of just
  one
• The ciphertext of one round becomes the entire
  input for the second iteration
• Employs a total of 48 iterations in its
  encryption (3 iterations times 16 rounds)
• The most secure versions of 3DES use different
  keys for each round

102
Advanced Encryption Standard (AES)

• Approved by the NIST in late 2000 as a
  replacement for DES
• Process began with the NIST publishing
  requirements for a new symmetric algorithm and
  requesting proposals
• Requirements stated that the new algorithm had to
  be fast and function on older computers with
  8-bit, 32-bit, and 64-bit processors

103
Advanced Encryption Standard (AES)

• Performs three steps on every block (128 bits) of
  plaintext
• Within step 2, multiple rounds are performed
  depending upon the key size
• 128-bit key performs 9 rounds
• 192-bit key performs 11 rounds
• 256-bit key uses 13 rounds

104
Hardening with Asymmetric Encryption Algorithms

• The primary weakness of symmetric encryption
  algorithm is keeping the single key secure
• This weakness, known as key management, poses a
  number of significant challenges
• Asymmetric encryption (or public key
  cryptography) uses two keys instead of one
• The private key typically is used to encrypt the
  message
• The public key decrypts the message

105
Hardening with Asymmetric Encryption Algorithms
106
Rivest Shamir Adleman (RSA)

• Asymmetric algorithm published in 1977 and
  patented by MIT in 1983
• Most common asymmetric encryption and
  authentication algorithm
• Included as part of the Web browsers from
  Microsoft and Netscape as well as other
  commercial products
• Multiplies two large prime numbers

107
Diffie-Hellman

• Unlike RSA, the Diffie-Hellman algorithm does not
  encrypt and decrypt text
• Strength of Diffie-Hellman is that it allows two
  users to share a secret key securely over a
  public network
• Once the key has been shared, both parties can
  use it to encrypt and decrypt messages using
  symmetric cryptography

108
Elliptic Curve Cryptography

• First proposed in the mid-1980s
• Instead of using prime numbers, uses elliptic
  curves
• An elliptic curve is a function drawn on an X-Y
  axis as a gently curved line
• By adding the values of two points on the curve,
  you can arrive at a third point on the curve

109
Understanding How to Use Cryptography

• Cryptography can provide a major defense against
  attackers
• If an e-mail message or data stored on a file
  server is encrypted, even a successful attempt to
  steal that information will be of no benefit if
  the attacker cannot read it

110
Understanding Cryptography Strengths and
Vulnerabilities

• Cryptography is science of scrambling data so
  it cannot be viewed by unauthorized users, making
  it secure while being transmitted or stored
• When the recipient receives encrypted text or
  another user wants to access stored information,
  it must be decrypted with the cipher and key to
  produce the original plaintext

111
Symmetric Cryptography Strengths and Weaknesses

• Identical keys are used to both encrypt and
  decrypt the message
• Popular symmetric cipher algorithms include Data
  Encryption Standard, Triple Data Encryption
  Standard, Advanced Encryption Standard, Rivest
  Cipher, International Data Encryption Algorithm,
  and Blowfish
• Disadvantages of symmetric encryption relate to
  the difficulties of managing the private key

112
Asymmetric Cryptography Strengths and
Vulnerabilities

• With asymmetric encryption, two keys are used
  instead of one
• The private key encrypts the message
• The public key decrypts the message

113
Digital Signatures

• Asymmetric encryption allows you to use either
  the public or private key to encrypt a message
  the receiver uses the other key to decrypt the
  message
• A digital signature helps to prove that
• The person sending the message with a public key
  is who they claim to be
• The message was not altered
• It cannot be denied the message was sent

114
Digital Certificates

• Digital documents that associate an individual
  with its specific public key
• Data structure containing a public key, details
  about the key owner, and other optional
  information that is all digitally signed by a
  trusted third party

115
Certification Authority (CA)

• The owner of the public key listed in the digital
  certificate can be identified to the CA in
  different ways
• By their e-mail address
• By additional information that describes the
  digital certificate and limits the scope of its
  use
• Revoked digital certificates are listed in a
  Certificate Revocation List (CRL), which can be
  accessed to check the certificate status of other
  users

116
Certification Authority (CA)

• The CA must publish the certificates and CRLs to
  a directory immediately after a certificate is
  issued or revoked so users can refer to this
  directory to see changes
• Can provide the information in a publicly
  accessible directory, called a Certificate
  Repository (CR)
• Some organizations set up a Registration
  Authority (RA) to handle some CA, tasks such as
  processing certificate requests and
  authenticating users

117
Understanding Public Key Infrastructure (PKI)

• Weaknesses associated with asymmetric
  cryptography led to the development of PKI
• A CA is an important trusted party who can sign
  and issue certificates for users
• Some of its tasks can also be performed by a
  subordinate function, the RA
• Updated certificates and CRLs are kept in a CR
  for users to refer to

118
The Need for PKI
119
Description of PKI

• Manages keys and identity information required
  for asymmetric cryptography, integrating digital
  certificates, public key cryptography, and CAs
• For a typical enterprise
• Provides end-user enrollment software
• Integrates corporate certificate directories
• Manages, renews, and revokes certificates
• Provides related network services and security
• Typically consists of one or more CA servers and
  digital certificates that automate several tasks

120
PKI Standards and Protocols

• A number of standards have been proposed for PKI
• Public Key Cryptography Standards (PKCS)
• X509 certificate standards

121
Public Key Cryptography Standards (PKCS)

• Numbered set of standards that have been defined
  by the RSA Corporation since 1991
• Composed of 15 standards detailed on pages 318
  and 319 of the text

122
X509 Digital Certificates

• X509 is an international standard defined by the
  International Telecommunication Union (ITU) that
  defines the format for the digital certificate
• Most widely used certificate format for PKI
• X509 is used by Secure Socket Layers
  (SSL)/Transport Layer Security (TLS), IP Security
  (IPSec), and Secure/Multipurpose Internet Mail
  Extensions (S/MIME)

123
X509 Digital Certificates
124
Trust Models

• Refers to the type of relationship that can exist
  between people or organizations
• In the direct trust, a personal relationship
  exists between two individuals
• Third-party trust refers to a situation in which
  two individuals trust each other only because
  each individually trusts a third party
• The three different PKI trust models are based on
  direct and third-party trust

125
Hardening Physical Security with Access Controls

• Adequate physical security is one of the first
  lines of defense against attacks
• Protects equipment and the infrastructure itself
• Has one primary goal to prevent unauthorized
  users from reaching equipment to use, steal, or
  vandalize

126
Hardening Physical Security with Access Controls

• Configure an operating system to enforce access
  controls through an access control list (ACL), a
  table that defines the access rights each subject
  has to a folder or file
• ACLs are also configured on network devices to
  permit or deny packets to the network.
• Access control also refers to restricting
  physical access to computers or network devices

127
Controlling Access with Physical Barriers

• Most servers are rack-mounted servers
• A rack-mounted server is 175 inches (445 cm) tall
  and can be stacked with up to 50 other servers in
  a closely confined area
• Rack-mounted units are typically connected to a
  KVM (keyboard, video, mouse) switch, which in
  turn is connected to a single monitor, mouse, and
  keyboard

128
Controlling Access with Physical Barriers

• In addition to securing a device itself, you
  should also secure the room containing the device
• Two basic types of door locks require a key
• A preset lock (key-in-knob lock) requires only a
  key for unlocking the door from the outside
• A deadbolt lock extends a solid metal bar into
  the door frame for extra security
• To achieve the most security when using door
  locks, observe the good practices listed on pages
  345 and 346 of the text

129
Controlling Access with Physical Barriers

• Cipher locks are combination locks that use
  buttons you push in the proper sequence to open
  the door
• Can be programmed to allow only the code of
  certain people to be valid on specific dates and
  times
• Basic models can cost several hundred dollars
  each while advanced models can run much higher
• Users must be careful to conceal which buttons
  they push to avoid someone seeing the combination
  (shoulder surfing)

130
Limiting Wireless Signal Range

• Use the following techniques to limit the
  wireless signal range
• Relocate the access point
• Add directional antenna
• Reduce power
• Cover the device
• Modify the building

131
Reducing the Risk of Fires

• Systems can be classified as
• Water sprinkler systems that spray the room with
  pressurized water
• Dry chemical systems that disperse a fine, dry
  powder over the fire
• Clean agent systems that do not harm people,
  documents, or electrical equipment in the room

132
Types of Security Policies
133
Types of Security Policies
134
Acceptable Use Policy (AUP)

• Defines what actions users of a system may
  perform while using computing and networking
  equipment
• Should have an overview regarding what is covered
  by this policy
• Unacceptable use should also be outlined

135
Understanding Identity Management (continued)

• Four key elements
• Single sign-on (SSO)
• Password synchronization
• Password resets
• Access management

136
Understanding Identity Management (continued)

• SSO allows user to log on one time to a network
  or system and access multiple applications and
  systems based on that single password
• Password synchronization also permits a user to
  use a single password to log on to multiple
  servers
• Instead of keeping a repository of user
  credentials, password synchronization ensures the
  password is the same for every application to
  which a user logs on

137
Understanding Identity Management (continued)

• Password resets reduce costs associated with
  password-related help desk calls
• Identity management systems let users reset their
  own passwords and unlock their accounts without
  relying on the help desk
• Access management software controls who can
  access the network while managing the content and
  business that users can perform while online

138
Auditing Privileges

• You should regularly audit the privileges that
  have been assigned
• Without auditing, it is impossible to know if
  users have been given too many unnecessary
  privileges and are creating security
  vulnerabilities

139
Usage Audit

• Process of reviewing activities a user has
  performed on the system or network
• Provides a detailed history of every action, the
  date and time, the name of the user, and other
  information

140
Usage Audits (continued)
141
Privilege Audit

• Reviews privileges that have been assigned to a
  specific user, group, or role
• Begins by developing a list of the expected
  privileges of a user

142
Escalation Audits

• Reviews of usage audits to determine if
  privileges have unexpectedly escalated
• Privilege escalation attack attacker attempts to
  escalate her privileges without permission
• Certain programs on Mac OS X use a special area
  in memory called an environment variable to
  determine where to write certain information