What is Fail2ban?
Fail2Ban is a free, open-source software tool that protects servers from brute-force attacks and other types of malicious activity. It monitors log files for suspicious activity and blocks IP addresses that are trying to access a server.
Why use Fail2ban?
There are several reasons to use Fail2ban:
- Prevents brute force attacks on services
- Reduces server load from automated login attempts
- Provides an extra layer of security beyond firewalls
- Notify when there is an IP is ban/unban through SMTP, Webhook
How it works
- Fail2Ban scans log files for suspicious activity, such as too many access, failed attempts through access or error files
- Fail2Ban creates a firewall rule to block the IP address that is causing the suspicious activity
- The IP address is blocked for a specified amount of time
Basic understanding Fail2ban
Jails:
- Jails serve as rule sets that dictate the conditions under which an IP address should face a ban which defined by monitoring log files
- Predefined jail configurations can be found in
/etc/fail2ban/jail.confwithin Fail2ban
Filters:
- Filters are instrumental in scrutinizing service logs using regex patterns to identify potentially malicious activities, like intrusion attempts.
- These filters are typically stored in
/etc/fail2ban/filter.d/
Actions:
- Actions encompass a range of responses, from IP address bans to notifications and the execution of custom scripts
- Commands outlining ban or unban procedures for IP addresses are typically housed in
/etc/fail2ban/action.d/
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