Index

Operating System

Introduction

15.1 The Security Problem


Figure 15.1 - Standard security attacks.

15.2 Program Threats

15.2.1 Trojan Horse

15.2.2 Trap Door

15.2.3 Logic Bomb

15.2.4 Stack and Buffer Overflow


      #include 
      #define BUFFER_SIZE 256
      
      int main( int argc, char * argv[ ] )
      {
          char buffer[ BUFFER_SIZE ];
          
          if( argc < 2 )
              return -1;
          else {
              strcpy( buffer, argv[ 1 ] );
              return 0;
          }
      }

Figure 15.2 - C program with buffer-overflow condition.


Figure 15.3 - The layout for a typical stack frame.


Figure 15.4 - Hypothetical stack frame for Figure 15.2, (a) before and (b) after.

15.2.5 Viruses


Figure 15.5 - A boot-sector computer virus.

15.3 System and Network Threats

15.3.1 Worms


Figure 15.6 - The Morris Internet worm.

15.3.2 Port Scanning

15.3.3 Denial of Service

15.4 Cryptography as a Security Tool

15.4.1 Encryption


Figure 15.7 - A secure communication over an insecure medium.

15.4.1.1 Symmetric Encryption

15.4.1.2 Asymmetric Encryption


Figure 15.8 - Encryption and decryption using RSA asymmetric cryptography

15.4.1.3 Authentication

15.4.1.4 Key Distribution


Figure 15.9 - A man-in-the-middle attack on asymmetric cryptography.

15.4.2 Implementation of Cryptography

15.4.3 An Example: SSL

15.5 User Authentication

15.5.1 Passwords

15.5.2 Password Vulnerabilities

15.5.3 Encrypted Passwords

15.5.4 One-Time Passwords

15.5.5 Biometrics

15.6 Implementing Security Defenses

15.6.1 Security Policy

15.6.2 Vulnerability Assessment

15.6.3 Intrusion Detection

15.6.4 Virus Protection

15.6.5 Auditing, Accounting, and Logging

Tripwire Filesystem ( New Sidebar )

15.7 Firewalling to Protect Systems and Networks


Figure 15.10 - Domain separation via firewall.

15.8 Computer-Security Classifications ( Optional )

15.9 An Example: Windows XP ( Optional )