Metasploit is a popular penetration framework for cybersecurity enthusiasts.

Wireshark is a popular network analysis tool for anyone looking to get into networking or cybersecurity.

Nmap is a popular tool that is used to tell which ports are open on a network with the intent of looking for vulnerable hosts.

Snort is an open source Intrusion Prevention System (IPS) that can also be used as a packet sniffer or a packet logger.

Angry IP Scanner is something that is used to scan for open or available IP addresses within a given range. It can also resolve hostnames, determine MAC addresses, and scan ports.

This is a popular website that is used to tell the reputation of an IP address, website, or hash value.

Process mnonitor is an advanced monitoring tool for Windows that shows real-time file system, registry, and process/thread activity.

Sift Workstation is a collection of free and open-source incident response and forensics tools designed to perform detailed digital forensic examinations in a variety of settings.

Kali Linux is an open-source, Debian- based Linux ditribution geared towards various information security tasks such as Penetration Testing, Security Research, Computer Forensics, and Reverse Engineering.

Shodan is the world's first search engine for internet connected devices.

Cisco Talos Threat Intelligence is a tool that can be used to verify the reputation of an IP address or hostname. There is also a vulnerability and TTP blog.

Any Run is a free interactive malware analysis service that can be used to sandbox.