ClamAV (antivirus) is a free software, cross-platform antimalware toolkit able to detect many types of malware, including viruses.

It was developed for Unix and has third party versions available for AIX, BSD, HP-UX, Linux, macOS, OpenVMS, OSF (Tru64), Solaris and Haiku.

[7] Trend Micro claimed that Barracuda's utilization of ClamAV infringes on a software patent for filtering viruses on an Internet gateway.

[11] ClamAV includes a command-line scanner, automatic database updater, and a scalable multi-threaded daemon running on an anti-virus engine from a shared library.

[16] In other words, the On-Access Scanner can detect and prevent access to malicious files based on the verdict received from Clamd.

[16] By default, it operates in "notify-only mode", alerting users of any threats detected without actively blocking file access.

[16] In order to use ClamOnAcc, users need to first run clamd and then start the On-Access Scanner as root (to leverage its kernel event detection and intervention capabilities).

[16] Users can run multiple instances of ClamOnAcc simultaneously with different configurations, allowing for customized protection settings for various directories.

[16] ClamOnAcc (v0.102+) is a client application that operates alongside clamd (the ClamAV daemon), to perform On-Access Scanning.

These can include mail exchange programs, files on Samba shares, or packets of data passing through a proxy server.

On Linux and BSD desktops ClamAV provides on-demand scanning of individual files, directories or the whole PC.

Working alongside the Eudora Internet Mail Server program, Counteragent scans emails for viruses using ClamAV and also optionally provides spam filtering through SpamAssassin.

The build process is simple and provides basic functionality, including library, the clamscan utility, the clamd daemon, and freshclam for update.