ClamWin is free, open source antivirus software for Microsoft Windows. It provides a graphical user interface to the ClamAV (Clam AntiVirus) engine.

Features

• Scanning scheduler (only effective with user logged in).
• Automatic virus database updates on a regular basis.
• Standalone virus-scanner.
• Context menu integration for Windows Explorer.
• Add-in for Microsoft Outlook.
• A portable version that can be used from a USB flash drive.

Real-time scanning
ClamWin does not yet automatically scan files as they are read and written. This feature is planned for inclusion in the next major version update and has been claimed to be in development since at least 10 December 2005. For users of older systems, it is currently possible to add this functionality by using Winpooch.
The non-affiliated project Clam Sentinel is an add-on that provides a real-time scanning capability to ClamWin.

Effectiveness

ClamWin suffers from poor detection rates and its scans are slow and less effective than some other antivirus programs. For example, ClamWin failed to detect almost half of the trojan horses, password stealers, and other malware in AV-Test.org's "zoo" of malware samples.
In the 1 - 21 June 2008 test performed by Virus.gr, ClamWin version 0.93 detected 54.68% of all threats and ranked 37th out of 49 products tested; the best scored over 99%.
In the 10 August-05 September 2009 test performed by Virus.gr, ClamWin version 0.95.2 detected 52.48% of all threats and ranked 43 out of 55 products tested; the best scored 98.89%.