OSSEC is an Open Source Host-based Intrusion Detection System that performs log analysis, file integrity checking, policy monitoring, rootkit detection, real-time alerting and active response.
sshfp generates DNS SSHFP records from SSH public keys. sshfp can take public keys from a known_hosts file or from scanning the host's sshd daemon.
Online tool to test webserver allowed http methods
Linux distros for vulnerablity exploration training
mitmproxy is an interactive, SSL-capable man-in-the-middle proxy for HTTP with a console interface.