Linux Security Checklist• Add Users and Passwords• Read, Write, and Execute Permissions• Protect root• Use Trusted Software• Get Software Updates• Use Secure Applications• Use Restrictive Firewalls• Enable Only Services You Need
Linux Security Checklist• Limit Access to Services• Check Your System• Monitor Your System• Use SELinux• The centos-announce List (http://lists.centos.org/)• Red Hat Security Alerts (www.redhat.com/security)
Using the Security Level ConfigurationWindow• Set up a basic firewall using the Security Level Configuration window.• Trusted Services— You can open access to ports associated with your network interfaces to provide the services you want to make available from your system. Some services, such as Samba, require that multiple ports be open.• Other Ports—You can allow access to any other port numbers by adding them to the ‘‘Other ports’’ box
Using the ssh, sftp, and scp commands• Three commands you can use with the SSH service are ssh, sftp, and scp. Remote users use the ssh command to log in to your system securely. The scp command lets remote users copy files to and from a system. The sftp command provides a safe way to access secure SFTP sites.
Understanding Attack Techniques• Denial of Service (DOS)• Distributed Denial of Service (DDOS)• Intrusion Attacks
Protecting against Denial-of- Service Attacks• attack attempts to crash your computer or at least degrade its performance to an unusable level.• Mailbombing - e-mail-filtering tool• Smurf Amplification Attack (flooding your Internet connection) - The best fix is to contact the organization being used as a relay and inform them of the abuse.
Protecting against Distributed DOS Attacks• much harder to initiate and nearly impossible to stop.• The best way to defend yourself is to contact your ISP and see if it can filter the traffic at its border routers.
Protecting against Intrusion Attacks• Intrusion attacks focus on exploiting weaknesses in your security• Disabling Network Services• Securing Servers with SELinux• Protecting Web Servers with Certificates and Encryption