CompTIA Security+ Exam Notes

CompTIA Security+ Exam Notes
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Friday, October 24, 2025

Censys.io: Internet-Wide Scanning for Security Professionals

 Censys.io

Censys.io is a powerful cybersecurity intelligence platform designed to help security professionals, researchers, and analysts discover, monitor, and assess internet-connected assets. Here's a detailed breakdown of how it works and why it's valuable for host discovery and security analysis:

What Is Censys.io?
Censys.io is a search engine and data platform that continuously scans the public internet to catalog exposed devices, servers, and services. It provides structured, searchable data about:
  • IP addresses
  • Open ports and services
  • SSL/TLS certificates
  • Software versions
  • DNS records
  • Geolocation and routing data
How Censys Works
Censys uses internet-wide scanning to probe every IPv4 address and popular domain names. It performs:
  • Protocol handshakes to identify running services
  • TLS certificate parsing for security analysis
  • Port scanning across all 65,535 ports
  • Metadata enrichment using third-party sources like IPInfo and RouteViews
This data is then indexed and made available via:
  • A web interface for interactive search
  • An API for automation and integration
  • BigQuery and raw data formats for advanced analysis

Key Features
  • GeoIP Information: Uses IP geolocation APIs to provide location data for hosts.
  • Service Summaries: Lists exposed services, ports, and protocols for each host.
  • Certificate Search: Tracks SSL/TLS certificates and their chains.
  • Web Properties: Identifies websites, APIs, and apps with detailed HTTP response data.
  • Advanced Query Language: Enables precise searches using structured fields like host.services.port or web.endpoints.banne.
Use Cases
  • Attack Surface Management: Identify and reduce exposed services and misconfigurations.
  • Threat Hunting: Discover vulnerable or suspicious systems.
  • Reconnaissance: Used by ethical hackers and penetration testers for OSCP and CEH prep.
  • Compliance & Monitoring: Track changes in internet-facing infrastructure over time.

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