Improving Email Security with Rspamd 4.2: Complete Guide

Rspamd 4.2 is a significant update of the open-source spam filtering system, designed to improve phishing detection, URL processing, attachment scanning, and the WebUI interface. This update is useful for system administrators and IT professionals who need a more efficient and secure spam filtering system.

The main improvement concerns the in-depth analysis of email attachments, with particular attention to SVG, XLSX, PPTX, and DOCX files. Rspamd can now detect suspicious elements such as external links, embedded scripts, macros, remote resources, and other content used in phishing campaigns.

• Advanced attachment analysis: Rspamd 4.2 can deeply examine SVG, XLSX, PPTX, and DOCX files to detect suspicious elements.
• Improved URL processing: Public suffix lookups are now about seven times faster, with improved support for complex domain suffix rules.
• Refined DKIM management: Messages with a valid DKIM signature get an additional advantage when the signing domain matches the sender's domain.
• WebUI improvements: Administrators can now more easily check the health of fuzzy storage, view improved Bayes statistics, monitor server latency and uptime, and identify version or configuration differences between servers in a cluster.
• Improved indexing for ClickHouse: New indexing features to speed up searches for senders, Message-IDs, IP addresses, URLs, subjects, and attachment hashes.
• Security and reliability fixes: Improvements in limits during the analysis of untrusted data and fixes for crashes and race conditions involving filtering maps.

For more details, check the official Rspamd 4.2 changelog.

Prerequisites

• Hardware: Server with at least 2 CPU cores and 4GB of RAM
• Software:
  • Linux operating system (Ubuntu, Debian, CentOS, etc.)
  • Rspamd 4.2 (available here)
  • Development libraries (gcc, make, autoconf, automake, libtool, pkg-config)
  • Additional libraries (libpcre3, libssl-dev, libhiredis-dev, libluajit-5.1-dev, libprotobuf-dev, libfuzzy-dev)
  • Database (Redis or ClickHouse for advanced features)

PROCEDURE: Upgrading to Rspamd 4.2

By the end of this guide, you will have correctly upgraded your Rspamd spam filtering system to version 4.2, benefiting from the new features and improvements.

• Access your server via SSH.
• Update the operating system and necessary dependencies:
  • For Debian/Ubuntu: sudo apt update && sudo apt upgrade -y
  • For CentOS/RHEL: sudo yum update -y
• Stop the Rspamd service: sudo systemctl stop rspamd
• Upgrade Rspamd to version 4.2:
• Check the Rspamd version to confirm the upgrade: rspamadm -V
• Examine the filtering rules execution order: rspamadm configdump -e

Verification and Troubleshooting

By the end of this guide, you will be able to test the correct functioning of Rspamd 4.2 and resolve any issues.

Functionality Testing

• Verify attachment analysis: Send an email with SVG, XLSX, PPTX, or DOCX attachments containing suspicious elements such as external links or scripts. Check that Rspamd identifies them correctly.
• Test URL processing: Send emails with complex URLs and verify that the system processes them quickly and according to the specified domain rules.
• Examine the filtering rules execution plan: Use the command rspamadm configdump -e to verify the execution order of the rules and ensure that dependencies are managed correctly.

Troubleshooting

• Issues with attachment analysis: If Rspamd does not detect suspicious elements in attachments, verify that the analysis modules are correctly configured and updated.
• Slowness in URL processing: If URL processing is slow, check the system configuration and ensure that public suffix lookups are optimized.
• Errors in DKIM signatures: If DKIM signatures are not recognized correctly, verify the DKIM configuration and ensure that domains are correctly matched.
• Issues with the filtering rules execution plan: If rules are not executed in the expected order, review the dependency configuration and use the command rspamadm configdump -e to diagnose the problem.
• Stability issues: If you encounter crashes or race conditions, ensure that parsing limits for untrusted data are set correctly and update Rspamd to the latest version.

With this guide, you have learned how to leverage the new features of Rspamd 4.2 to improve your spam filtering capabilities and detect phishing. You are now ready to implement these improvements in your system.

To get started, make sure to upgrade Rspamd to version 4.2 and verify the new attachment analysis features, such as SVG, XLSX, PPTX, and DOCX. Use the command rspamadm configdump -e to inspect the filtering rules execution order.

• Explore the new Bayes statistics and monitor server latency via the WebUI.
• If you use ClickHouse, take advantage of the new indexing options to speed up searches.
• Verify the integrity of your system with DKIM improvements and security fixes.