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CONTROLS & PROTECTION MECHANISMS. Today’s Reference: Whitman & Mattord, Management of Information Security , 2 nd edition, 2008 Chapter 9. Overview. Access controls Firewalls Intrusion Detection Systems (IDSs) Wireless Network Security Cryptography. Access Controls.

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Controls protection mechanisms

CONTROLS & PROTECTION MECHANISMS

Today’s Reference:

Whitman & Mattord, Management of Information Security, 2nd edition, 2008

Chapter 9


Overview
Overview

  • Access controls

  • Firewalls

  • Intrusion Detection Systems (IDSs)

  • Wireless Network Security

  • Cryptography


Access controls
Access Controls

  • Authentication – controlling a person’s access to a system

    • Barrier (i.e. login sequence) versus ongoing (intrusion detection)

    • Something you know

    • Something you have

    • Something you are (and something you produce, e.g. voice)

    • Includes biometrics which authenticate a user against known personal features (fingerprints, iris patterns, voice, etc)

    • Something you do (user behaviour profiling)

  • Authorisation – controlling a person’s access to features (software, data) within the system

    • Scoping each user’s permitted activities

    • Maybe individual or group-based

    • Can be specific to resources


Firewalls
Firewalls

  • Generations

    • 1: packet filtering

    • 2: application-level

    • 3: stateful inspection

    • 4: dynamic packet filtering

  • Architectures

    • Packet filtering routers

    • Screened-host firewalls

    • Dual-homed host firewalls

    • Screened-subnet firewalls


Intrusion detection systems
Intrusion Detection Systems

  • Host-based

    • Alerts administrator when files or folders change

    • Monitor host only

  • Network-based

    • Monitor network traffic

    • Alerts administrator when patterns of network traffic change

  • Signature-based

    • Work like anti-virus software

    • Alerts administrator when ‘signature’ of attack is matched

  • Statistical-anomaly-based

    • Establishes baseline of what is ‘normal’ traffic

    • Alerts administrator when pattern is abnormal

  • Rule-based ‘never do this’

    • includes honeypots


Wireless network security
Wireless Network Security

  • Wired Equivalent Privacy (WEP)

    • basic level of security

    • several fundamental cryptological flaws

    • average home or small only

  • Wi-Fi Protected Access (WPA)

    • WPA is industry standard

    • increased capabilities for authentication, encryption, and throughput


Cryptography
Cryptography

  • Symmetric encryption methods

    • Substitution, Transposition, XOR, Vernam Cipher, One-time pad, and many others

    • the same key—a secret key—is used to encrypt and decrypt the message

    • Mono-alphabetic & poly-alphabetic ciphers

  • Asymmetric encryption

    • public key encryption (PKE)

    • uses two different keys. Either key can be used to encrypt or decrypt the message, but one must always be kept secret

  • Digital signatures

    • PKE used in reverse to give non-repudiation

  • Steganography

    • Hiding messages in graphics files


Controls protection mechanisms

Encryption & Decryption

Plain Text

Encryption

Cipher

from Sender

Secure

Cipher Text

Key Management

Plain Text

Decryption

Cipher

to Recipient


Symmetric encryption methods
Symmetric Encryption Methods

  • Substitution

    • One letter exchanged for another

    • Creates confusion

    • Mono-alphabetic or Poly-alphabetic

  • Transposition

    • Re-arrangement of letters

    • Creates diffusion

  • XOR

    • If 2 values are the same, you get “0”

    • If not, you get “1”

    • Process is reversible

      E.g. 1 0 1 0 0 0 1 0

      1 1 1 1 0 0 0 1

      __________________

      0 1 0 1 0 0 1 1


Controls protection mechanisms

Monoalphabetic cipher

Random

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

M N B V C X Z L K J H G F D S A P O I U Y T R E W Q

Keyword

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

S E C U R I T Y A B D F G H J K L M N O P Q V W X Z

Caesar

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

D E F G H I J K L M N O P Q R S T U V W X Y Z A B C

plaintext is ROSTRUM

ciphertext is URVWUXP


Controls protection mechanisms

Polyalphabetic Cipher

Alphabet No. 1

(offset by 3)

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

D E F G H I J K L M N O P Q R S T U V W X Y Z A B C

Alphabet No. 2

(offset by 15)

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

P Q R S T U V W X Y Z A B C D E F G H I J K L M N O

1 2 1 2 1 2 1 2 1

plaintext is GO FOR GOLD

ciphertext is JD IDU VRAG


Transposition ciphers
Transposition Ciphers

  • For example, every 4th letter

  • Modern transposition ciphers use a network or path diversity principle, so the diffusion is not just within-file but over the network via different paths

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3

THE RAIN IN SPAIN FALLS

4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3

MAINLY ON THE PLAIN

becomes

TANIL AYHAH ISNLI OEIEN

PFSNN PNRIA AMLTL


Vernam cipher
Vernam Cipher

  • The perfect substitution cipher

  • The original one-time pad

    Plaintext V E R N A M

    Numerics 21 4 17 13 0 12

    Random 76 48 16 82 44 3

    _________________

    Sum 97 52 33 95 44 15

    Mod 26 19 0 7 17 18 15

    Ciphertext T A H R S P


Breaking encryption
Breaking Encryption

  • (almost) All encryption is crackable…

    • Just need time and computing power

  • Brute force may not work because -

    • Number of alphabet combinations is 26 x 25 x 24 x 23 x etc which equals 4 x 1027

    • 4 000 000 000 000 000 000 000 000 000

    • If each alphabet takes 1 millionth of a sec (micro second) then all combinations would take 4 x 1021 secs

    • 4 x 1013 years !!!!

  • EXCEPT…

    • The one-time pad is provably secure (if properly used)

    • but it is not easy to use properly


Public key encryption
Public Key Encryption

  • Known as Asymmetric encryption

  • 2 keys, one public, one private, linked mathematically, one to encrypt & one to decrypt

  • Uses large prime numbers

  • “mathematically infeasible” to derive private key from public key

  • Advantages

    • no need to tell anyone your private key

    • no need for key distribution

    • no need for a key for each pair of people

  • Not used to encrypt messages, as it is generally slower than secret-key encryption

  • Used to encrypt other keys (as in PGP) and to authenticate sender


Digital signatures
Digital Signatures

  • Reverses the role of private & public keys

  • Effectively unique to the document

    • uses a cryptographically-robust hash function

  • Unforgeable (without the sender’s private key)

  • not re-usable (due to message-specific hash)

  • document unalterable

  • undeniable


What you need to know
What you Need to Know

  • A basic level of detail about all of the security technologies in the previous slides.