ClamAV
also: Clam AntiVirus, clamd, clamscan
ClamAV is a free, open-source antivirus engine designed to detect trojans, viruses, malware, and other malicious threats on Linux and other Unix-like systems.
ClamAV (Clam AntiVirus) is widely used as a server-side malware scanner, particularly in mail servers and file-sharing systems. It provides real-time protection and on-demand scanning capabilities without requiring a graphical interface.
The core of ClamAV is clamd, a daemon process that continuously monitors for threats, while clamscan is a command-line tool for manual virus scans. You can scan a single file with clamscan /path/to/file or an entire directory recursively with clamscan -r /path/to/directory.
ClamAV maintains an updated virus signature database that can be refreshed automatically using freshclam, ensuring detection of the latest known threats. It's commonly integrated with mail systems like Postfix and Exim, and with content management systems to scan uploaded files automatically.