Find Service banners from a domain

Censys

Internet asset and certificate search engine

FOFA

Internet asset search and mapping engine

Nmap

Network mapping and port scanning tool

Shodan

Search exposed internet-connected services

Wireshark

Network protocol analyzer

ZoomEye

Cyberspace search engine for exposed assets

Aquatone

HTTP host screenshotting and clustering

BinaryEdge

Paid internet-scan and asset discovery API

Criminal IP

CTI search engine scoring IPs and domains for threats

Driftnet

Internet-scan intelligence for domains and IPs

Hunter.how

Search engine for internet-exposed hosts and devices

LeakIX

Exposed-database and misconfig search engine

Metasploit Framework

Penetration testing and exploit framework

Naabu

a fast port scanner designed for reliable host and service discovery

Netcat

TCP/UDP networking utility

ONYPHE

ONYPHE internet-wide scanning platform

Quake

Qihoo 360 internet-asset search engine

Rapid7 Project Sonar

Rapid7 free internet-scan datasets

Smap

Passive Nmap replacement using Shodan data

TShark

Command-line packet analysis tool

Uncover

a query tool that aggregates results from internet-wide search engines and as

WebScout

IP and host intelligence for threat research

ZGrab2

Internet-scale application-layer scanner

Zabbix

Open-source infrastructure monitoring

hping3

Packet crafting and network testing

tcpdump

Command-line packet capture utility