Cybersecurity

1. Dehashed—View leaked credentials.
2. SecurityTrails—Extensive DNS data.
3. DorkSearch—Really fast Google dorking.
4. ExploitDB—Archive of various exploits.
5. ZoomEye—Gather information about targets.

6. Pulsedive—Search for threat intelligence.
7. GrayHatWarfare—Search public S3 buckets.
8. PolySwarm—Scan files and URLs for threats.
9. Fofa—Search for various threat intelligence.
10. LeakIX—Search publicly indexed information.

11. DNSDumpster—Search for DNS records quickly.
12. FullHunt—Search and discovery attack surfaces.
13. AlienVault—Extensive threat intelligence feed.
14. ONYPHE—Collects cyber-threat intelligence data.
15. Grep App—Search across a half million git repos.

16. URL Scan—Free service to scan and analyse websites.
17. Vulners—Search vulnerabilities in a large database.
18. WayBackMachine—View content from deleted websites.
19. Shodan—Search for devices connected to the internet.
20. Netlas—Search and monitor internet connected assets.

21. CRT sh—Search for certs that have been logged by CT.
22. Wigle—Database of wireless networks, with statistics.
23. PublicWWW—Marketing and affiliate marketing research.
24. Binary Edge—Scans the internet for threat intelligence.

25. GreyNoise—Search for devices connected to the internet.
26. Hunter—Search for email addresses belonging to a website.
27. Censys—Assessing attack surface for internet connected devices.
28. IntelligenceX—Search Tor, I2P, data leaks, domains, and emails.

29. Packet Storm Security—Browse latest vulnerabilities and exploits.
30. SearchCode—Search 75 billion lines of code from 40 million projects.

More tools : 

Wireshark - An open-source packet analyzer used for network troubleshooting, analysis, and protocol development.

Metasploit Framework - An open-source penetration testing framework that delivers the information needed to plan, test, and improve security defenses.

Nmap ("Network Mapper") - An open source tool for network exploration and security auditing.

Snort - An open-source intrusion detection system that can monitor network traffic in real-time.

John the Ripper - An open-source password-cracking tool.

OWASP Zap - An open-source web application security scanner.

Kali Linux - A pen-testing distribution with hundreds of tools for cybersecurity professionals.

OSSEC - An open-source, host-based intrusion detection system that performs log analysis, integrity checking, and more.

Aircrack-ng - An open-source suit of tools that can assess WiFi network security.

Burp Suite - A reliable and practical platform that provides security testing tools to identify vulnerabilities during web application testing.

SANS Investigative Forensic Toolkit (SIFT) - An open-source collection of forensic tools designed to provide digital forensic capabilities.

OpenVAS - Open Vulnerability Assessment Scanner is a full-featured vulnerability scanner.

Suricata - A high-performance network IDS, IPS, and network security monitoring engine.

SQLMap - An open-source penetration testing tool that automates the process of detecting and exploiting SQL injection flaws.

Cuckoo Sandbox - An open-source software for automated dynamic malware analysis.

Hashcat - An open-source password recovery tool that supports over 200 highly-optimized hashing algorithms.

NESSUS - A comprehensive vulnerability scanner.

Hydra - A fast and flexible password cracking tool.

Mitre ATT&CK - A globally accessible knowledge base of adversary tactics and techniques.

Splunk - A tool to make machine data accessible, usable, and valuable to everyone.

YARA - A tool designed to help malware researchers identify and classify malware samples.

MISP - Open-source Threat Intelligence Platform & Open Standards For Threat Information Sharing.

ClamAV - An open-source antivirus engine for detecting trojans, viruses, malware & other malicious threats.

Bro/Zeek - An open-source network security monitor.

Ghidra - A software reverse engineering (SRE) suite of tools developed by NSA's Research Directorate.

Tenable.io - Provides actionable insight into your entire vulnerability landscape including the cloud, your infrastructure, applications and more.

Moloch - An open-source tool designed for large-scale packet capture.

QualysGuard - A tool that provides cloud security, compliance and related services and is based on rapid detection and diagnostics.

OpenStego - An open-source software used for information hiding and digital watermarking.

Logstash - An open-source tool for managing events and logs.

Palo Alto Networks Prisma Cloud - Provides visibility across the cloud environment, helps to maintain compliance building security checks into your development pipeline.

Nikto - An open-source web server scanner that tests for dangerous files and outdated server software.

ModSecurity - An open source, cross-platform web application firewall (WAF) module.

Rapid7 Nexpose - A vulnerability management solution that handles the complete vulnerabililty lifecycle.

AlienVault OSSIM - An open-source security information and event management tool, providing event collection, normalization and correlation.

Graylog - An open-source, centralized log management solution built to open up the use of log data to more users in an enterprise.

Fail2Ban - An open-source intrusion prevention software framework that protects computer servers from brute-force attacks.

Ophcrack - A free open-source tool for cracking Windows passwords.

Security Onion - A free and open-source Linux distribution for threat hunting, enterprise security monitoring, and log management.

Cobalt Strike - A threat emulation tool that makes use of social engineering to challenge network security manoeuvres.

FireEye Security Suite - Provides comprehensive protection against advanced threats, zero-day attacks, and ransomware.

Sysdig Falco - An open-source behavioural activity monitor designed to detect anomalous activity in your applications.

Osquery - An open-source tool that exposes an operating system as a high-performance relational database.

CrowdStrike Falcon - A cloud-native endpoint security solution that stops breaches, including for workloads, and provides full spectrum visibility across your enterprise.

acunetix - An automatic web application security testing tool that audits web applications by checking for vulnerabilities like SQL Injection, Cross site scripting, and others.