1. CIT 140: Introduction to ITSlide #1 CSC 140: Introduction to IT File Security

2. CIT 140: Introduction to ITSlide #2 Questions What is security? Authentication –Users –Passwords –Groups Privacy Integrity Access Control –chmod

3. CIT 140: Introduction to ITSlide #3 What is Security? Security is the prevention of certain types of intentional actions from occuring in a system. –These potential actions are threats. –Threats that are carried out are attacks. –Intentional attacks are carried out by an attacker. –Objects of attacks are assets.

4. CIT 140: Introduction to ITSlide #4 Assets 1.Identity 2.Network bandwidth 3.Disk space 4.Confidential data

5. CIT 140: Introduction to ITSlide #5 Threats 1.Theft 2.Vandalism 3.Extortion 4.Con Games 5.Fraud

6. CIT 140: Introduction to ITSlide #6 Digital Threats: What’s Different Automation –Salami Attack from Office Space. Action at a Distance –Volodya Levin, from St. Petersburg, Russia, stole over $10million from US Citibank. Arrested in London. –Operators of CA BBS tried and convicted in TN court because TN had d/led pornography f/ CA. Technique Propagation –Criminals share techniques rapidly and globally.

7. CIT 140: Introduction to ITSlide #7 Authentication on UNIX Identity: username –Public knowledge –How would you find out someone’s username? Authentication: password –Secret –How would you find out someone’s password?

8. CIT 140: Introduction to ITSlide #8 Figuring out Passwords 1.Intentional disclosure –You tell someone your password. 2.Unintentional disclosure –Someone watches you type your password. –Someone finds where you wrote it down. 3.Guessing –Guess based on what you know about person. –Guess dictionary words + permutations. 4.Brute force –Try every combination of characters.

9. CIT 140: Introduction to ITSlide #9 Changing your Password Why? –Prevent it from being guessed. –Change periodically to avoid brute force attacks. How? –passwd

10. CIT 140: Introduction to ITSlide #10 Encryption-based Protection

11. CIT 140: Introduction to ITSlide #11 Access Control: Identity Access to system resources restricted Restrictions based on identity –User –Group –Anyone

12. CIT 140: Introduction to ITSlide #12 Access Control: Permissions Read –You can read the file with cat, more, etc. Write –You can modify the file with vi, OpenOffice, etc. Execute –You can run the file if it’s a program.

13. CIT 140: Introduction to ITSlide #13 Access Control

14. CIT 140: Introduction to ITSlide #14 Access Control: Directories Read –You can list directory contents with ls, etc. Write –You can create new files with touch, etc. –You can delete files with rm, etc. Execute –You can cd to the directory.

15. CIT 140: Introduction to ITSlide #15 Octal Codes for Access Control

16. CIT 140: Introduction to ITSlide #16 Access Control: Commands Determining File Access Privileges ls –l, ls –ld

17. CIT 140: Introduction to ITSlide #17 Access Control: Commands

18. CIT 140: Introduction to ITSlide #18 Access Control: Commands

19. CIT 140: Introduction to ITSlide #19 Access Control: Commands Changing File Access Privileges –chmod [options] octal-mode file –chmod [options] symbolic file

20. CIT 140: Introduction to ITSlide #20 Examples of chmod Command

21. CIT 140: Introduction to ITSlide #21 Access Control: chmod

22. CIT 140: Introduction to ITSlide #22 Access Control: chmod

23. CIT 140: Introduction to ITSlide #23 Access Control: chmod

24. CIT 140: Introduction to ITSlide #24 umask mask The access permission value on executable file or directory is computed by: file permission = 777 – mask Current Value of the mask: $ umask 777 $ Access Control: Commands

25. CIT 140: Introduction to ITSlide #25 Special Access Bits The Set-User-ID (SUID) Bit –Command runs with privileges of file owner when. –chmod 4xxx file-list –chmod u+s file-list The Set-Group-ID (SGID) Bit –Command runs with privileges of group owner. –chmod 2xxx file-list –chmod g+s file-list The Sticky Bit –Prevents non-owners from removing/renaming files in dir. –chmod 1xxx file-list –chmod +t file-list

26. CIT 140: Introduction to ITSlide #26 Special Bits Examples SetUID Bit > ls -l /etc/passwd /usr/bin/passwd -rw-r--r-- 1 root root 1335 2005 /etc/passwd -rwsr-xr-x 1 root root 25464 2005 /usr/bin/passwd SetGID Bit > ls –l /usr/bin/wall -rwxr-sr-x 1 root tty 9784 2005 /usr/bin/wall Sticky Bit > ls -ld /var/tmp drwxrwxrwt 13 root root 4096 2005 /var/tmp

27. CIT 140: Introduction to ITSlide #27 Special Access Bits