 Chapter 14 – Security Engineering 1 Chapter 12 Dependability and Security Specification 1

Threat Types  Interception  May be hard to detect  Interruption  Denial of service  Modification  Fabrication Chapter 12 Dependability and Security Specification 2

Levels of Attack  Levels  Application  Infrastructure  OS  Database  Web server  Network  GUI  Attack on infrastructure may be more likely  Better known vulnerabilities Chapter 12 Dependability and Security Specification 3

Design Guidelines  #1 Base security decisions on an explicit security policy  Stated, overall goal (what, not how)  Examples  Only physicians registered with system can view data  Only creator of a record can modify it  All transactions must be logged Chapter 12 Dependability and Security Specification 4

Design Guidelines  #2 Avoid single point of failure  Single Point of Failure: One aspect of a system that if it were to fail, the entire system would be fail.  Examples / solutions  Database (if only one server) – mirrored site  Web server (if only one server) – redundant server  Data records loss – keep log so that data can be recreated  Layered protection (“defense in depth”0  Like multiple protections of a house  Passwords: login, password, IP, biometrics,… Chapter 12 Dependability and Security Specification 5

Design Guidelines  #3 Fail securely – If there is a failure, resulting condition should not be less secure  Example:  Failure to find a file in a web directory - you need to block browsing of web directories  Reboot OS in “safe mode” – you still need to require logon to access data, functionality Chapter 12 Dependability and Security Specification 6

Design Guidelines  #4 Balance security and usability  Example:  Excessively difficult password systems will force users to document them (on sticky notes, text files…) Chapter 12 Dependability and Security Specification 7

Design Guidelines  #5 Log user actions  Example:  Track logon attempts, including passwords, IP address – if analyzed can lead to attacker  Track who attempts to change data (but is denied) Chapter 12 Dependability and Security Specification 8

Design Guidelines  #6 Use redundancy and diversity to reduce risk  Example:  Redundancy – second copy of web site, database,  Diversity – different version of software Chapter 12 Dependability and Security Specification 9

Design Guidelines  #7 Validate all inputs  SQL Injection – response to a form field that, when inserted into an SQL command can cause undesired actions in the database  Command:  Select * from Users where id=‘xxxx’  Field:  1’ ; DROP TABLE users; select ‘a  Solution: escape string Chapter 12 Dependability and Security Specification 10

Design Guidelines  #8 Compartmentalize assets  Example:  Voter targeting stem:  All clients could have accessed same database, tables.  This was separated into separate database per customer Chapter 12 Dependability and Security Specification 11

Design Guidelines  #9 Design for deployment – plan for clear configuration  Example:  Software inside of a wireless router (Airport Express)  Default security mode  Default DHCP ranges  Default network names Chapter 12 Dependability and Security Specification 12

Design Guidelines  #10 Design for recoverability  Steps  Features to view all configuration  Minimize default privileges  Require intentional setting  Localize configuration settings  (Not everywhere in system)  Provide easy ways to fix vulnerabilities  Software update mechanisms  Auto check for updates Chapter 12 Dependability and Security Specification 13

Design Guidelines  #11 – Limit menus, options to only what user has permissions for Chapter 12 Dependability and Security Specification 14

Survivability  Ability to continue to deliver service even if under attack Chapter 12 Dependability and Security Specification 15

Survivability Strategies  Resistance  Recognition  Recovery Chapter 12 Dependability and Security Specification 16

Activity  Discuss what you would do to address the guidelines discussed tonight  Systems  Facebook  Healthcare management system  School grade records system Chapter 12 Dependability and Security Specification 17

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