ClamAV

The Internet is full of malware threats and if you're running an email server or other services, you will definitely want to protect everything against attacks. ClamAV offers a simple, yet effective solution. This lightweight utility can scan for viruses, trojans, worms and many other threats and eliminate them from your system. It is designed more for network administrators, rather than regular users, which should explain the lack of a user interface. However, the software is quite fast, even when scanning large amounts of files, which makes it an excellent solution for mail gateways.

ClamAV is available as a free and open-source utility, for Windows Linux and Mac OS X. Its setup package is small, so you can download it in no time, even with a slow Internet connection. The installation process is just as fast, but you will have to download and install the software's definition files separately.

As previously mentioned, there is no user interface to speak of. Several executables can be found in the software's installation folder, but you can't just run them normally. The software can be controlled through the system's command prompt (CMD), where you have to type in commands.

Running the software's executables has to be done from the command prompt. Just navigate to its installation folder and type in the name of the executables, along with command-line arguments if you need to. For example, you can simply run the main executable to start scanning the current folder, but you can also scan a specific folder, by adding its path, after the executable's name. Of course, you can run other executable as well, to set up automatic signature updates or perform other operations.

ClamAV's multi-threaded scanning capabilities are something you can definitely rely on. You can definitely expect a high performance level, when scanning emails or attachments. Furthermore, the software is quite versatile when it comes to file formats. It can verify documents, images, archives and many other file types.

Protecting a mail server from malicious attacks can be much simpler when using ClamAV.