clamd

ClamD, or clamd, is the daemon component of ClamAV, an open-source antivirus engine. It runs in the background as a service and provides on-demand scanning capabilities to other applications. Clamd is commonly deployed on servers such as mail gateways, file servers, and network appliances to enable real-time or on-demand scanning of files, email attachments, and data streams. It accepts connections from local or remote clients through a UNIX domain socket and, if enabled, a TCP port, and it communicates using ClamAV’s command protocol. Clamd relies on the ClamAV virus signature databases, which are updated by the freshclam updater and loaded into memory on startup or after updates.

Operation and configuration: Clamd loads the virus databases from a configured database directory and maintains in-memory indexes to accelerate scans. It is configured via a clamd.conf file, where administrators can set options such as LocalSocket (the path to the UNIX socket), TCPSocket or TCPPort (to enable network access), DatabaseDirectory (location of signatures), PidFile, and logging settings. The service supports multiple concurrent connections and can be restricted to socket-based access for security. When network access is enabled, access should be restricted by firewall rules because clamd’s protocol does not include built-in authentication.

Usage and integration: Clamd is designed for integration with other software and pipelines, including mail transfer agents, web gateways, and file scanning workflows. Clients communicate with the daemon to request scans or health checks and to retrieve statistics. Regular database updates are essential for effective protection, and administrators should ensure that clamd reloads its databases after updates. Administrators should monitor clamd for errors and configure the service to run with least privilege, typically under a dedicated user account.