When hardening a Cisco firewall that has an internet connection, it’s crucial to implement proper security measures. Here are steps with example commands to properly harden a Cisco firewall:

  1. Update Firmware:
    • Ensure your firewall is running the latest firmware version to benefit from security patches and bug fixes.
  2. Configure Management Access:
    • Restrict management access to authorized IP addresses only:

firewall(config)# access-list management permit tcp host <management-ip> any eq ssh
firewall(config)# access-group management in interface <interface>

3.Enable AAA:

  • Implement Authentication, Authorization, and Accounting (AAA) for secure access control:

firewall(config)# aaa new-model
firewall(config)# aaa authentication login default local
firewall(config)# aaa authorization exec default local
firewall(config)# aaa accounting exec default start-stop group radius

4.Implement Secure Administrative Accounts:

  • Create individual user accounts with strong passwords for administrative access:

firewall(config)# username <username> privilege 15 secret <password>

5.Enable Logging and Monitoring:

  • Configure logging to capture events and potential security threats:

firewall(config)# logging host <syslog-server-ip>
firewall(config)# logging trap <severity-level>
firewall(config)# logging buffered <buffer-size>

6.Implement Access Control Lists (ACLs):

  • Define and apply ACLs to control traffic flow:

firewall(config)# access-list <acl-name> permit <source-ip> <destination-ip> <protocol>
firewall(config)# access-group <acl-name> in interface <interface>

7.Enable Intrusion Prevention System (IPS):

  • Activate IPS to detect and prevent network intrusions:

firewall(config)# ips signature-category
firewall(config-ips-category)# category all
firewall(config-ips-category)# retired true
firewall(config-ips-category)# exit
firewall(config)# ips signature-definition
firewall(config-ips)# signature 2004 12 12
firewall(config-ips)# signature 3000 10 12
firewall(config-ips)# exit
firewall(config)# interface <interface>
firewall(config-if)# ips inline fail-open

8.Configure Anti-Spoofing:

  • Prevent IP spoofing by configuring anti-spoofing rules:

firewall(config)# interface <interface>
firewall(config-if)# ip verify unicast reverse-path

9.Enable Threat Detection:

  • Enable threat detection features to monitor and protect against potential attacks:

firewall(config)# threat-detection basic-threat
firewall(config)# threat-detection scanning-threat
firewall(config)# threat-detection statistics

10.Regularly Update Firewall Policies:

Review and update firewall policies to ensure they align with your network security requirements.

Remember to customize the commands according to your network environment and specific configurations. It’s essential to regularly review and update your security measures to stay protected against emerging threats.