• Introduction to Internet and System Security
  • Introduce computer system security terminology
  • Discuss some common Internet and system security issues
  • Introduce some common classes of attack
• Why Security?
  • Can you afford not to have security?
    • Costs of security breaches can be massive
  • Costs of security breaches can be due to
    • Business stolen by competitors
    • Loss of reputation due to publicity of the breach
    • Network service degraded, or stopped
    • You might be prosecuted
• What is Computer Security?
  • Keeping anyone from doing things that you do not want them to do with, or from your data
• What Are We Protecting?
  • Stored Information
  • Accuracy of Information
  • Information Value
  • Access to External Services
  • Access to Internal Services
  • The Enterprise's Privacy
• Who Are We Protecting It From?
  • Hackers
    Typically young hobbyists; gain access via external network connections.
  • Criminal Intruders
    They typically have more resources than hackers
  • Corporate Raiders
    They may have lots of resources!
  • Insiders
    Very dangerous; they are already past the first barrier
  • Contractors
    They present similar problems as insiders, and possess less reason for loyalty
• Security Model
  • Authenticity
    • Stop unauthorized access to information
    • Stop unauthorized alterations to a device's configuration
  • Privacy
    • Stop interception/disclosure of information to unauthorized parties
  • Integrity
    • Computer system assets and transmitted information must be modifiable only by authorized parties
  • Availability
    • Computer system assets must be available to authorized parties when needed
• Security Model Responsibilities
  • Personal: The "user" level
    • Countermeasures are the responsibility of system administrators and individual users
  • Interior: Threats from within your enterprise
    • Deployment of countermeasures are the responsibility of the system/network administrator
  • Exterior: Threats derived from external network connections
    • The network administrator is responsible for countermeasures
• Attacks: Stealing or Guessing Passwords
  • Password Stealing
    • Knowing or guessing passwords, which provides a "Front Door" into the system
  • Knowledge of the password implies a valid (i.e. authorized) user
  • Networks make the situation worse
    • Passwords are frequently sent "in the clear" (unencrypted) across the net
  • Social engineering is the easiest way into a system
• Attacks: Bugs and Backdoors
  • Many operating systems and network software implementations have known weaknesses
    • Sendmail has had various problems
    • Finger has been known to provide entrance
    • Windows NT still supports dangerous protocols (LanMan) in order to keep backward compatibility
  • Usually are fixed in subsequent releases
    • Many machines are still running old versions without the bug fixes
    • Sometimes bug fixes just create new pathways in
  • Good software engineering practices in operating system and network software design would help
    • Orange Book attempts to deal with this issue
• Attacks: Protocol Failures
  • Many protocols are not designed to be secure
    • The TCP/IP protocol suite was designed for a network of "trusted hosts"
    • Trusted Computing Base (TCB) = trusted (host + user + path/route)
  • Failures deny applications the chance to do the right thing
    • E.g. IP source address spoofing
    • TCP session stealing
  • Cryptographic protocols
    • Key distributions may be insecure
    • Keys may be broken or compromised (enigma)
• Attacks: Information Leakage
  • The finger protocol gives information about individual users
    • Tells who is currently logged in
    • Helps with password guessing
  • The Domain Name System (DNS)
    • Address (A) records
      • Map host names to IP addresses
      • Provide target lists for attackers
    • Pointer (PTR) records
      • Map IP addresses to host names
      • Attacker's host IP addresses can pretend to be a trusted host
    • Nslookup, Whois, and Whatis also provide detailed information
• Attacks: Denial of Service
  • Brute Force
    • Filling up a machine's disk (or partition) via email or FTP
    • Hogging a server's CPU by creating numerous (or rogue) processes
    • Filling up an enterprise's internal network with bogus traffic
      • ICMP echo request messages
      • SYN/ACK attacks
    • Crack (password guessing program)
  • Routing and routing protocols
    • Disruption of communications
      • Corrupting routing tables
      • Changing host subnet masks
• The Security Policy
  • A security policy is
    • A formal definition of an enterprise's stance on security - on what is and is not allowed
  • Formulating a security policy
    • Essential for any enterprise that has security concerns
    • Requires a thorough understanding of the potential threats
    • Need to determine countermeasures
    • Usually includes a security audit of existing systems
    • A number of good (and not so) tools exist
• Security Policy Details
  • It should consist of a formal document
  • No two enterprises have exactly the same documents
    • Risks and costs vary
    • Documents may be subsidiary to other documents
  • Two basic stances
    • Everything not explicitly prohibited is permitted (permissive)
    • Everything not explicitly permitted is prohibited (restrictive)
• Security Policy: Legal Issues
  • A certain level of security may be a legal requirement
    • Data Protection Act (Europe)
    • Electronic Communications Privacy Act (U.S.)
  • You may be legally restricted in what activities you can monitor
    • Surveillance is often allowed only with a court order
    • Classified areas may differ
  • Will you be able to prosecute a criminal intruder?
    • Evidence of a break-in must be admissible in court
    • Computer logs may not be admissible
• Summary
  • Four threats to security
    • Masquerade
    • Interception
    • Modification
    • Interruption
  • Security policy objectives maintain
    • Authenticity
    • Privacy
    • Integrity
    • Availability
  • A security policy is essential
  • Lack of, or ineffective security costs money

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Last modified: Sat Nov 30 13:18:35 PST 2002