Firewall Blocklist Formats: MikroTik, Cisco, pfSense, Nginx, Apache and Linux

A blocklist is only useful if it can be deployed safely. Network teams often need the same abuse data in several formats: router address lists, firewall ACLs, web server deny rules, shell scripts, and plain text feeds.

MikroTik RouterOS

MikroTik address lists are practical for edge blocking because firewall rules can reference the list by name. RouterOS v7 timeouts help temporary entries age out naturally.

Cisco and enterprise firewalls

Cisco IOS, IOS-XE, and ASA environments often need ACL or object-group formats. The main risk is rule size and ordering, so large lists should be deployed with staged testing and rollback steps.

pfSense and OPNsense

URL table aliases work well when the firewall can periodically fetch a plain text list. This is a good fit for an active IP feed because refreshes can be automated.

Linux servers and web stacks

iptables, nftables, Nginx, and Apache formats are useful when blocking happens close to the application. Web server rules protect HTTP services, while nftables and iptables stop traffic earlier.

Deployment checklist

1. Use the active 30-day list for production enforcement.
2. Test the export format on a staging device or low-risk server.
3. Keep a backup of the previous firewall configuration.
4. Monitor dropped traffic after deployment.
5. Document ASN exclusions and business exceptions.

Related IPToBlock resources

• Browse the active IP blocklist
• Download firewall-ready blocklists
• Read the latest security news and CVE briefs