CrowdSec

CrowdSec SAS in Montrouge is the odd one in this category and belongs here anyway.

It is open source under MIT, it runs on servers rather than laptops, and it works by reading your logs, spotting attack behaviour, and blocking the addresses behind it — then sharing that signal with everyone else running CrowdSec, so an address hammering a server in Poland is blocked in Portugal before it arrives. Think of it as Fail2ban with a community behind it and a modern architecture.

It does not scan files, it does not protect laptops, and comparing it with ESET on malware detection is comparing two different jobs. What it does do is remove a whole class of noise from internet-facing infrastructure for nothing, with paid plans only for the enriched threat feed and enterprise features. The catch is the usual open-source one: you run it, you configure the scenarios, and the quality of what you get out depends on the attention you put in.

What CrowdSec does well

• Free and open source under MIT, with paid tiers only for the enriched feed
• Community threat intelligence: one attacker blocked everywhere at once
• Built for servers and internet-facing services
• French company, EU processing

Where CrowdSec falls short

• Not endpoint anti-malware; it does not protect laptops
• You run and tune it yourself
• Young company compared with the rest of this list

Standout feature. The network effect turned defensive: every participant blocking an attacker makes the block faster for everyone else.