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

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

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.

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

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

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.

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?

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.

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

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

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

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.

CIT 140: Introduction to ITSlide #13 Access Control

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.

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

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

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

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

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

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

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

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

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

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

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

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

CIT 140: Introduction to ITSlide #27 Special Access Bits