Passive Recon List

Passive reconnaissance is the act of conducting reconnaissance without generating noise.

Shodan

Shodan is a search engine that lets users search for various types of servers (webcams, routers, servers, etc.) connected to the internet using a variety of filters.

https://www.shodan.io/www.shodan.io

Virustotal

Analyse suspicious files, domains, IPs and URLs to detect malware and other breaches, automatically share them with the security community.

VirusTotalVirusTotal

Subdomainfinder

Subdomain Finder is a scanner that scans an entire domain to find as many subdomains as possible.

Subdomain Finder - C99.nlsubdomainfinder.c99.nl

DNSDumpster

DNSDumpster.com is a FREE domain research tool that can discover hosts related to a domain. Finding visible hosts from the attackers perspective is an important part of the security assessment process.