POWBlock is a high-performance, C-based proof-of-work gateway designed to protect web servers from automated bot traffic and DDoS attacks by requiring clients to solve cryptographic challenges.

Key Points

• POWBlock functions as a lightweight, ~1MB standalone binary that integrates with existing reverse proxies like Varnish, Nginx, and HAProxy.
• The software forces clients to perform SHA-256 or SHA-512 hashing before granting access, effectively filtering out automated scrapers and request-flood attacks.
• It is hardware-optimized to fit within CPU L3 caches, enabling it to handle over 250,000 requests per second with minimal system resource consumption.
• The tool has been battle-tested in production environments since early 2025, reportedly blocking 99% of automated spam for a high-traffic origin server.
• It is distributed as shareware, offering core features for free while requiring a $50 lifetime license for enterprise-level or commercial use.

Why it Matters

By providing a modular, low-overhead defense mechanism, POWBlock allows administrators to secure their infrastructure without the performance penalties associated with monolithic security suites. This approach empowers developers to maintain control over their own traffic stacks while effectively mitigating sophisticated bot-driven threats.