Protect servers from brute force attacks with Fail2Ban. Use when a user asks to block repeated failed login attempts, protect SSH, secure web servers from brute force, or ban malicious IPs automatically.
Scanned 5/27/2026
Install via CLI
openskills install TerminalSkills/skills---
name: fail2ban
description: >-
Protect servers from brute force attacks with Fail2Ban. Use when a user asks
to block repeated failed login attempts, protect SSH, secure web servers from
brute force, or ban malicious IPs automatically.
license: Apache-2.0
compatibility: 'Linux'
metadata:
author: terminal-skills
version: 1.0.0
category: devops
tags:
- fail2ban
- brute-force
- ssh
- security
- firewall
---
# Fail2Ban
## Overview
Fail2Ban monitors log files for failed authentication attempts and bans offending IPs using iptables/nftables. Protects SSH, Nginx, Apache, Postfix, and any service with log-based authentication.
## Instructions
### Step 1: Install
```bash
sudo apt install fail2ban
sudo systemctl enable fail2ban
```
### Step 2: Configure
```ini
# /etc/fail2ban/jail.local — Custom configuration (never edit jail.conf)
[DEFAULT]
bantime = 1h
findtime = 10m
maxretry = 5
banaction = iptables-multiport
[sshd]
enabled = true
port = ssh
maxretry = 3
bantime = 24h
[nginx-http-auth]
enabled = true
port = http,https
maxretry = 5
[nginx-botsearch]
enabled = true
port = http,https
maxretry = 2
bantime = 7d
```
### Step 3: Monitor
```bash
sudo fail2ban-client status # list active jails
sudo fail2ban-client status sshd # show banned IPs
sudo fail2ban-client set sshd unbanip 1.2.3.4 # unban
sudo fail2ban-client set sshd banip 5.6.7.8 # manual ban
```
## Guidelines
- Always create jail.local — jail.conf gets overwritten on updates.
- Start conservative: 5 retries, 1h ban. Adjust based on logs.
- For modern alternative with community threat sharing, consider CrowdSec.
- Use `fail2ban-regex` to test custom filters before deploying.
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