added fail2ban integration

plugins/fail2ban/fail2ban.md

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+# Fail2Ban + Krawl Integration
+
+## Overview
+
+This guide explains how to integrate **[fail2ban](https://github.com/fail2ban/fail2ban)** with Krawl to automatically block detected malicious IPs at the firewall level using iptables. Fail2ban monitors Krawl's malicious IP export and applies real-time IP bans.
+
+## Architecture
+
+```
+Krawl detects malicious IPs
+         ↓
+Writes to malicious_ips.txt
+         ↓
+Fail2ban monitors the file
+         ↓
+Filter matches IPs using regex
+         ↓
+Iptables firewall blocks the IP
+         ↓
+Auto-unban after bantime expires
+```
+
+## Prerequisites
+
+- Linux system with iptables
+- Fail2ban installed: `sudo apt-get install fail2ban`
+- Krawl running and generating malicious IPs
+- Root/sudo access
+
+## Installation & Setup
+
+### 1. Create the Filter Configuration [krawl-filter.conf](krawl-filter.conf)
+
+Create `/etc/fail2ban/filter.d/krawl-filter.conf`:
+
+```ini
+[Definition]
+failregex = ^<HOST>$
+```
+
+**Explanation:** The filter matches any line that contains only an IP address (`<HOST>` is fail2ban's placeholder for IP addresses). In this case, we use **one IP per row** as a result of the Krawl detection engine for attackers.
+
+### 2. Create the Jail Configuration [krawl-jail.conf](krawl-jail.conf)
+### 2.1 Krawl is on the same host
+Create `/etc/fail2ban/jail.d/krawl-jail.conf` and replace the `logpath` with the path to the krawl `malicious_ips.txt`: 
+
+```ini
+[krawl]
+enabled = true
+filter = krawl
+logpath = /path/to/malicious_ips.txt
+backend = auto
+maxretry = 1
+findtime = 1
+bantime = 2592000
+action = iptables-allports[name=krawl-ban, port=all, protocol=all]
+```
+### 2.2 Krawl is on a different host
+
+If Krawl is deployed on another instance, you can use the Krawl API to get malicious IPs via a **curl** command scheduled with **cron**.
+
+```bash
+curl http://your-krawl-instance/dashboard-path/api/get_banlist?fwtype=raw -o malicious_ips.txt
+```
+
+#### Cron Setup
+
+Edit your crontab to refresh the malicious IPs list:
+
+```bash
+sudo crontab -e
+```
+
+Add this single cron job to fetch malicious IPs every hour:
+
+```bash
+0 * * * * curl http://your-krawl-instance/dashboard-path/api/get_banlist?fwtype=raw -o /tmp/malicious_ips.txt
+```
+
+Replace the `krawl-jail.conf` **logpath** with `/tmp/malicious_ips.txt`.
+
+### 3. Reload Fail2Ban
+
+```bash
+sudo systemctl restart fail2ban
+```
+
+Verify the jail is active:
+
+```bash
+sudo fail2ban-client status krawl
+```
+
+## How It Works
+
+### When an IP is Added to malicious_ips.txt
+
+1. **Fail2ban detects the new line** in the log file (via inotify)
+2. **Filter regex matches** the IP address pattern
+3. **maxretry check:** Since maxretry=1, ban immediately
+4. **Action triggered:** `iptables-allports` adds a firewall block rule
+5. **IP is blocked** on all ports and protocols
+
+### When the 30-Day Rotation Occurs
+
+Your malicious IPs file is rotated every 30 days. With `bantime = 2592000` (30 days):
+
+If you used `bantime = -1` (permanent), old IPs would remain banned forever even after removal from the file. This option is not recommended because external IPs can rotate and are unlikely to be static.
+
+## Monitoring
+
+### Check Currently Banned IPs
+
+```bash
+sudo fail2ban-client status krawl
+```
+
+### View Fail2Ban Logs
+
+```bash
+sudo tail -f /var/log/fail2ban.log | grep krawl
+```
+
+## Management Commands
+
+### Manually Ban an IP
+
+```bash
+sudo fail2ban-client set krawl banip 192.168.1.100
+```
+
+### Manually Unban an IP
+
+```bash
+sudo fail2ban-client set krawl unbanip 192.168.1.100
+```
+
+
+### Clear All Bans in Krawl Jail
+
+```bash
+sudo fail2ban-client set krawl unbanall
+```
+
+### Restart the Krawl Jail Only
+
+```bash
+sudo fail2ban-client restart krawl
+```
+
+## References
+
+- [Fail2Ban Documentation](https://www.fail2ban.org/wiki/index.php/Main_Page)
+- [Fail2Ban Configuration Manual](https://www.fail2ban.org/wiki/index.php/Jail.conf)
+- [Iptables Basics](https://www.digitalocean.com/community/tutorials/iptables-essentials-common-firewall-rules-and-commands)

plugins/fail2ban/krawl-filter.conf

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+[Definition]
+failregex = ^<HOST>$

plugins/fail2ban/krawl-jail.conf

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+[krawl]
+enabled = true
+filter = krawl
+logpath = /path/to/malicious_ips.txt ; update this path to where your krawl malicious IPs are logged
+backend = auto
+maxretry = 1
+findtime = 1
+bantime = 2592000 ; 30 days 
+action = iptables-allports[name=krawl-ban, port=all, protocol=all]