History of Math According to Stephen Hawking

History of Math According to Stephen Hawking

Linux Security 2016 GenCyber JMU Bootcamp for High School Teachers OS Security In General Applications Services OS OS Kernel CPU, I/O

Linux Some common OS security topics Manage user accounts OS update Enable firewall Disable guest account Monitor logs Check file permissions Manage services

2 Ubuntu Security Applications Services OS OS Kernel CPU, I/O Linux

Some common OS security topics Manage user accounts OS update Enable firewall Disable guest account Monitor logs Check file permissions Manage services 3

Manage User Accounts Manage User Accounts Manage User Accounts OS Updates OS Updates Ubuntu Firewall Install Gufw

Ubuntu Firewall Disable guest account Save the change Need to restart Set password policies Set password history Set account policy

Monitor logs Check file permissions For a file, Can its owner read/write/execute it? Can other users in the same group read/write/execute it? Can other users in the system read/write/execute it? Check file permissions

View file permission, ls l myfile Change file permission: chmod Set audit policy Manage services The Linux File System

Every user has a home directory (default location for his/her files) Find out what the current users home directory is: echo $HOME Associated with every shell is a location in the file system called the working directory

Find out what the current working directory is: pwd Listing Files and Directories To see what files and directories are in the current working directory use the ls command: ls

Most commands take options that affect their behaviour: ls -l show a long listing ls -a show all files and directories ls -la show a long listing of all files and directories Creating, Removing, and Changing Directories To create a new directory (in the current working directory) use the mkdir command: mkdir foo

To change the current working directory use the cd command: cd . go to the current directory cd .. go to the parent directory cd foo go to the foo directory cd go to the users home directory To remove an empty directory use the rmdir command:

rmdir foo Absolute and Relative Paths Relative specify a file or directory relative to the current directory cd foo cd ../..

Absolute specify a file or directory starting from the top (root) of the file system cd / cd /home/elvis/foo The Linux File System A hierarchy of files and directories: / bin/dev/

etc/ home/ alice/ memos/ bob/ report.doc root/

fred/ tmp/ Important Linux Directories /bin common commands (e.g. ls and ps) /boot files used at boot time

/dev files representing access points to system I/O devices (e.g. terminals, printers, disks, CDs) /etc system configuration files

/home user home directories /proc information about system resources /root home directory for root user

/sbin administrative command Viewing and Editing Files Many ways to display the contents of text files: cat command (no scrolling)

more and less commands (scrolling) Many editors available: pico/nano (simple) vi

emacs Permissions Define access rights of various users to each file

View file permissions with the ls l command: drwxr-xr-x 2 elvis elvis 4096 Jan 12 18:32 Desktop -rw-rw-r-- 1 elvis elvis 102 Jan 13 14:37 numbers Note: 10 permission bits

Bit 1 (leftmost): file type Bits 2-4 : owners permissions (read, write, and execute) Bits 5-7 : groups permissions (read, write, and execute) Bits 8-10 : worlds permissions (read, write, and execute) Permissions (cont)

Read (file) view contents Read (directory) see what files and subdirectories it contains Write (file) change contents of , rename, or delete the file Write (directory) add files or subdirectories

Execute (file) run the file as a program Execute (directory) cd into the directory Modifying Permissions Use the chmod command: chmod 777 file

rwxrwxrwx chmod 755 file rwxr-xr-x chmod 644 file rw-r--r-- chmod 600 file

rw------- chmod 000 file --------- Modifying Permissions (cont) Use the chmod command with +/-:

a = all u = user g = group o = other (world) Examples:

chmod a-w file r-xr-xr-x chmod go-rwx file r-x------ chmod a+w file rwx-w--w-

Moving, Copying, and Removing Files Moving: mv file1 file2 Copying: cp file1 file2

Removing: rm file1 User database Stored in /etc/passwd Each line contains the account information for a single user:

Username UID GID Home directory Default shell

Shadowed and Salted Passwords Linux protects the password hashes: Password hashes usually stored in a protected file: /etc/ shadow A salt value is used

Password hashes can still be cracked Securing a Linux Server Best Practices:

Patches Accounts Audit Services Firewall Malware defense Mandatory Access Controls Security guides and tools Linux Patching As with Windows, patches for the Linux OS

and its applications and libraries are released often Tools: Red Hat: up2date Debian (including Ubuntu): apt-get/aptitude RHEL, Fedora, CentOS: yum Ubuntu Patching o Tools: - Update Manager (GUI) - apt-get/aptitude - Third party tools

(e.g. http://www.manageengine.com/products/security-manager) Apt-get Can be used to: Install/Remove/Update packages Example: Sudo apt-get install emacs Accounts Delete/disable unnecessary accounts Users settings GUI useradd/userdel commands

Never have any account with no/default password Change all passwords to good ones Account policies: /etc/pam.d/common-password password policies chage command - used to view/set password expiration options of individual users Logging Most log files are text files located in /var/log: auth.log account log in and log out lastlog binary file used by lastlog program to display

most recent log in of all users wtmp binary file used by last program to display listing of last users logged in Certain applications also store their logs in subdirectories in /var/log: Apache, mysql, etc. Reviewing Logs Manually inspect log files System Log Viewer GUI Automated tools:

Logwatch http://www.logwatch.org Logcheck/Logsentry http:// sourceforge.net/projects/sentrytools/ Others Services Delete/disable unnecessary services and programs

The services GUI Starting/stopping of all services is controlled by scripts in /etc/rcX.d (where X is a run level 0-6) Use invoke-rc.d program to start/stop services immediately sudo invoke-rc.d apache2 stop Use update-rc.d program to enable/disable a service at boot time Services (cont) Secure all necessary services Dont install untrusted software

Consider the source Consider the signature Host-based Firewall Uncomplicated Firewall (ufw) firewall configuration utility $ sudo ufw allow ssh/tcp $ sudo ufw logging on $ sudo ufw enable $ sudo ufw status Rules and configuration stored in /etc/ufw

Firewall (cont) Block all unnecessary/unauthorized traffic Allow traffic to necessary services Other network security options: TCP Wrappers network access control list PortSentry protect against port scans http://sourceforge.net/projects/sentrytools/ Port scan attack detector (psad) http://www.cipherdyne.org/psad/

Malicious Software Defence Clam (http://www.clamav.net/lang/en/download/packages/pac kages-linux/) Avast! (http://www.avast.com/linux-home-edition) AVG (http://free.avg.com/in-en/download.prd-alf)

Chkrootkit (http://www.chkrootkit.org/) Mandatory Access Controls Users (thorough file permissions) can define discretionary access controls (DAC) on files Mandatory Access Controls (MAC) are rules enforced by the system regardless of the users DAC Several On-going Projects:

Security-Enhanced Linux GRSecurity Linux Intrusion Detection System Rule-Set Based Access Control SELinux Project originally developed by National Security Agency to implement Mandatory Access Controls within the Linux Kernel Incorporated into 2.6 Linux kernel

System Checks DAC then MAC policy before granting access to a resource Ubuntu supports SELinux (but it is not installed by default) Bastille Linux (cont) An interactive Linux-hardening tool See https://help.ubuntu.com/community/BastilleLinux Helps check/configure:

File permissions Account security System auditing Services Mail server Web server FTP server Firewall

Linux Security Guides Many are available Ubuntu Community: https://help.ubuntu.com/community/Security Summary Best Practices:

Patches Accounts Audit Services Firewall Malware defense Mandatory Access Control Security guides and tools (i.e. Bastille)

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