freshclam

Freshclam is the virus database updater for ClamAV, a cross-platform open-source antivirus toolkit. Its primary role is to download and install the latest ClamAV signatures so that the ClamAV scanner can detect newly identified malware and variants. Freshclam can run as a background updater or be invoked manually.

Operation and scope: Freshclam retrieves updated signature files from ClamAV mirrors. Core components typically downloaded include main.cvd and daily.cvd, along with other auxiliary databases such as bytecode.cld as applicable. Updates are stored in the ClamAV database directory (commonly /var/lib/clamav on Linux systems) and are used by clamd or the clamscan tool. The updater verifies downloads using checksums and signatures to ensure integrity and authenticity. After a successful update, a running ClamAV daemon (clamd) can be signaled to reload its database.

Configuration and usage: Freshclam is configured via a configuration file (freshclam.conf or, on some systems, /etc/freshclam.conf). Options control the database location, which update mirrors to use (DatabaseMirror or DNS-based mirror information), proxy settings, logging, and update frequency. Administrators can run freshclam directly to perform an immediate update or enable it as a scheduled task through systemd timers, cron jobs, or the package’s service unit (for example, clamav-freshclam). The updater typically runs automatically in environments where ClamAV is deployed, ensuring ongoing protection without manual intervention.

Platform considerations and limitations: Freshclam is available on major platforms supported by ClamAV, including various Linux distributions and Windows. Network access and proper mirror configuration are required for automatic updates. In some environments, proxies or firewalls may require configuration to permit TLS connections to update mirrors.

See also: ClamAV, clamd, virus signatures, database updates.