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Introduction To Linux Security
This document provides an introduction to Linux security. It covers turning off unnecessary servers and services, limiting access to needed servers using IPTables, updating the system regularly, and reading Linux log files. The document recommends keeping daemons and services disabled or bound to localhost when possible, using tools like netstat, IPTables, and log checking utilities to monitor open ports and system activity. It concludes with a question and answer section and recommends additional security resources.
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Introduction To Linux Security
- 1. Introduction to LinuxSecurity Introduction to Linux Security Republic Polytechnic Thursday 2 nd September 2004 By Michael Boman <[email protected]>
- 2. What we willcover: Turning off unnecessary servers and services Limit exposure of needed servers and services using IPTables Updating the system Reading Linux log files Q & A
- 3. Turning off xinetdlaunched services Locate the relevant file in /etc/xinetd.d Change “no” to “yes” in the “disable” field Restart xinetd service xinetd restart
- 4. Controlling Daemons Temporaryturn a daemon off service <daemon-name> stop Permanently removing a daemon from automatically starting at boot up chkconfig –del <daemon-name> Daemons start/stop scripts are stored in /etc/init.d
- 5. Who opened thatport? Use netstat to locate the application that opened a particular port netstat -tunl -t = tcp -u = udp -n = don't resolve -l = listen only
- 6. Limit access torequired daemons What can you do when you actually need that service? Bind the service to localhost (ip address 127.0.0.1), if possible Enable IPTables and control access to the particular service
- 7. Keeping the systemup-to-date All systems becomes vulnerable as time passes and new vulnerabilities are discovered Always keep your system up-to-date to avoid unnecessary time spent on recovering from a intrusion
- 8. Linux log filesLog files are generally located in /var/log Syslog is the daemon that controls and create the log files Use a tool like “log check” to limit the amount of lines of logs to read through
- 9. Advanced Techniques Usea file integrity checker like “tripwire” to keep an eye at changed files Use a Network IDS like “snort” to monitor attacks from the network
- 10. Questions? Got anyquestions? Now is the time to ask them!
- 11. Recommended reading materialSecurity Focus www.securityfocus.com Linux Security www.linuxsecurity.org The Linux Documentation Project www.tldp.org IPTables www.netfilter.org Snort Network Intrusion Detection Software www.snort.org