Control Computers

Studying Cyber Attacks

Attack Scenarios

  • Mostly study possible attacks

  • Study potential or actual attacks to show a new risk(likelihood & loss)

    • Goals, resources required, how it happened, collateral results, and recommended mitigation

Attack case studies

  • review actual attacks

  • attack reports

Resources Required:

  • Skills /Training

  • Personnel

  • Equipment

  • Preparation Time

  • Timing Constraint

Access Control Strategies

4 Strategies:

  • Islands: Resources are only accessible on that “island”

  • Vaults: A process has the right to use resources within a much larger repository; access control on a computer with checks its access permissions

  • Puzzles: A process uses secret or hidden information to retrieve particular data items. Cryptography; Kerckhoff/Shannon

  • Patterns: Data and programs made available to a process are compared against patterns associated.

An Island

  • Everything else is brought from elsewhere

  • A process can execute its instructions in RAM & modify variables in RAM

    • It can only use resources brought into its RAM

    • It can’t access anything else

A Vault

  • We gain things from the vault only if allowed

    • someone/something restricts access

    • Least privilege:

  • A bank safe box only we have a key

  • Can’t retrieve or modify any other boxes

  • Computer access control - a process can retrieve a file or print data if granted the right permissions.

Puzzles

  • Protect data by presenting a puzzle

  • Security through obscurity (relying on the secrecy of design or hidden details)

  • Strong puzzles use cryptography

Open Design: Basic Principle

  • We open our systems for third-party analysis to help ensure their effectiveness.

  • Kerckhoff’s Principle (attackers already know everything) and crypto design

  • Shannon’s Maxim: “The enemy knows the system.”

Pattern Matching

  • In Anti-Virus software

    • searches the computer for patterns found in viruses

    • Must be updated continuously for new viruses

  • Biometrics

    • Compare reading against a stored pattern

    • Problems: False Positives and false negatives

Chain of Control

  • We must never run programs that violate or bypass our security policy.

Subverting the Chain of Control

  • At BIOS, we may

    • Boot a different OS from a CD-ROM or a USB drive

    • The other OS doesn’t enforce access restrictions

  • Inside the OS, we may

    • install a privileged (admin) program

    • Trick an authorized user into leaking sensitive files.

Personal Computer Evolution

  • 1970’s: PCs ran one program at a time

    • Microprocessor CPUs didn’t support multitasking

  • 1980’s: Programs politely took turns

    • Allowed several windows to be open at once

    • Illusion of multitasking

  • 1990’s: Multitasking in desktop computers

    • Microprocessor CPUs support multitasking

    • Unix on PCs Windows NT

Operating System Protections

  • Adapted to desktop OSes during 1990’s

  • OS security features

    • Processes much take turns

    • Processes are assigned differently from RAM

    • User-oriented Interface and access controls

Sharing Data

  • The problem: Allow two processes to share data stored in RAM

    • Isolate processes from each other

      • This prevents one process from damaging the other one.

  • OS provides a separate data section

    • All shared data resides in this separate section

Constructing a Security Plan

  • Security Plan is detailed assessment

  • The plan contains the details

    • List of assests

    • Full risk Assessment

    • Prioritized list of risks

    • Security Requirements

    • Implementation - a list of security controls

Security Plan: Process Protection

  • Goals

    • Processes share the CPU

    • Processes may share control sections

    • Processes don’t share RAM except by request

  • Risk

    • A process monopolizes the CPU

    • A process reads or writes RAM that shouldn’t

Policy and Implementation

  • Six policy statements

    • Specifies security to be arranged by the dispatcher

    • Specifies when things should happen

  • Security Controls

    • All are functional controls provided by software

    • Some are steps in the dispatcher procedure

    • Others are features of how security is applied.