Instiq

6System security

Practice questions →Glossary →
  • 6.1Packet Filtering with iptables/firewalld

    Learn packet filtering with iptables/ip6tables and the higher-level firewalld (firewall-cmd) and ufw. Cover kernel parameters under /proc/sys/net/ipv4///proc/sys/net/ipv6/, the routing table, port redirection, /etc/services, and persisting rules with iptables-save/iptables-restore.

  • 6.2Configuring and Managing the OpenSSH Server

    Learn sshd configuration via /etc/ssh/sshd_config: host keys (/etc/ssh/ssh_host_*_key/ssh_host_*_key.pub), controlling root login with PermitRootLogin, public key auth with PubkeyAuthentication, restricting users with AllowUsers, and PasswordAuthentication.

  • 6.3Configuring and Managing OpenVPN

    Learn the fundamentals of VPN (Virtual Private Network) and the open-source implementation OpenVPN: the configuration directory /etc/openvpn/, the openvpn command used by both server and client, and the difference between the two common topologies, point-to-point and site-to-site.

  • 6.4Security Operations

    Learn the tools of day-to-day security operations: connectivity/scanning with netcat(nc/ncat) and nmap, packet filtering with iptables/firewalld, vulnerability advisory sources Bugtraq, CERT, and CIAC, intrusion prevention with fail2ban, the intrusion detection system (IDS) snort, and vulnerability scanners OpenVAS/OpenSCAP.