Linux comes with a firewall, just enable it.

For antivirus, you can use Clamav. ClamAV antivirus is the most popular antivirus software on the Linux platform. ClamAV is a free and open source product that supports multiple platforms, such as: Linux/Unix, MAC OS X, Windows, and OpenVMS. ClamAV is a command line tool based on virus scanning, but there is also a ClamTK tool that supports a graphical interface. ClamAV is mainly used by mail servers to scan mail. It has multiple interfaces to scan emails from mail servers, supporting file formats such as: ZIP, RAR, TAR, GZIP, BZIP2, HTML, DOC, PDF, SIS CHM, RTF, etc. ClamAV has an automatic database updater and can also be run from a shared library. The command line interface makes ClamAV run smoothly.

Malware detection tool: LMD Tool, its design concept is to target the threats faced in the most shared hosting environment. It uses threat data from intrusion detection systems at the network perimeter, extracts current malware that is frequently used in attacks, and generates signatures for detected malware. In addition, data threats also come from malware submitted by users through the LMD upload function and resources obtained from malware alliances. The signatures used by LMD are MD5 hashes and HEX pattern matching, and they can also be easily exported to other detection tools such as ClamAV.