Firejail is a SUID sandbox program that reduces the risk of security breaches by restricting the running environmentof untrusted applications using Linux namespaces and seccomp-bpf. Written in C, virtually no dependencies, runs on anymodern Linux system, with no daemon running in the background, no complicated configuration, and it's super lightweightand super secure, since all actions are implemented by the kernel. It includes security profiles for over 800 commonLinux applications. FireJail is recommended for running any app that may potential pose some kind of risk, such astorrenting through Transmission, browsing the web, opening downloaded attachments.

(Linux)

Open source GUI firewall for Linux, allowing you to block internet access for certain applications. Supports both simpleand advanced mode, GUI and CLI options, very easy to use, lightweight/ low-overhead, under active maintenance and backedby a strong community. Installable through most package managers, or compile from source.

ClamTk is basically a graphical front-end for ClamAV, making it an easy to use, light-weight, on-demand virus scannerfor Linux systems.

Locally checks for signs of a rootkit.

Open source intrusion prevention system capable of real-time traffic analysis and packet logging.