2023 – Jean's Blog

Suricata Performance: Resolving eBPF Bypass Failure via Manual Kernel Filter Compilation

Enabling eBPF (Extended Berkeley Packet Filter) bypass is the ultimate step in Suricata performance tuning. It allows the kernel to filter known-safe traffic (e.g., TLS data) before the packets reach the resource-intensive Userspace engine. However, this functionality often fails to work out-of-the-box.

Suricata IPS: Fixing Legitimate Traffic Drops by Disabling drop-invalid

I encountered a peculiar issue where my WordPress instance was unable to reach wordpress.org, and DokuWiki could not access its plugin repository. All standard network checks (wget, curl, DNS) worked fine, and no drops were registered by the standard firewall rules.

However, logging revealed a problem deep within the Intrusion Prevention System (IPS) layer.

OpenSSH Hardening Strategy: Auditing Policies and Mitigating Low-Strength Ciphers

OpenSSH ships with a default configuration that prioritizes high compatibility. However, this compatibility comes at a price: some of the included ciphers and algorithms may be outdated or contain known vulnerabilities. To strengthen the encryption and gain a transparent overview of known weaknesses, ssh-audit is the essential auditing tool.

Paperless-NGX Setup: Installation, Security, and NGINX Integration

When I read about paperless-ngx, I was immediately drawn to the idea of having all my documents indexed (via OCR) and centrally stored. With a proper tagging system, exporting my documents for my annual tax declaration should only take seconds.

Bogon Defense: Integrating Dynamic IP Blacklists into Suricata’s Reputation System

Bogon networks are IP address ranges that should never appear on the public internet, as they are either reserved or unassigned. Blocking these ranges is a fundamental and highly effective security measure. While this can be done with simple firewall rules, integrating the blocklist directly into the Suricata IP Reputation system is far more performant.

Suricata AF-Packet: Resolving VirtIO Non-Functionality via Checksum Offload Disablement

This article documents a two-part process: successfully upgrading Suricata to version 7 on Debian Bookworm and solving a critical stability issue required to run the AF-Packet IPS mode with high-performance VirtIO NICs in a virtual machine. Without this specific configuration, the IPS failed to function.

Automating IPS: Real-Time Suricata Rule Generation via Fail2ban Hook

In my last posts, I established a central syslog hub feeding Fail2ban and demonstrated Suricata as an intrusion prevention system (IPS). This final piece connects the two: feeding Suricata with the ban results from Fail2ban by creating a dynamic, external rule file.

Suricata Alert Analysis: Tuning Rules and Promoting Detection to Prevention

This is a follow-up to my last post in which I set up Suricata as an IPS. This article demonstrates how to effectively work with the Suricata engine—specifically, how I analyze its log output, silence unnecessary alerts, and promote specific detection rules to prevention rules.

Suricata IPS: Building a Transparent Network Defense Layer with AF-Packet Bridging

Suricata functions as a powerful engine for Network Intrusion Detection and Prevention (IDS/IPS). This guide demonstrates how to set up Suricata as a transparent Intrusion Prevention System (IPS) within a KVM environment by replacing the kernel bridge with the high-performance AF-Packet mechanism.

Automated Defense: Building a Central Log Hub for Fail2ban and External Firewall Integration

A very light-weight and efficient approach for consolidating logs centrally is by using rsyslog. My virtual machines all use rsyslog to forward their logs to a dedicated internal virtual machine, which acts as the central log hub. A fail2ban instance on this hub checks all incoming logs and sends a block command to an external firewall—a process helpful for automated security.