In the context of CompTIA PenTest+, Shodan and Censys are critical tools for Open Source Intelligence (OSINT) and passive reconnaissance. Unlike traditional search engines that index web content, these engines scan the entire internet to index metadata from connected devices, servers, and IoT syste…In the context of CompTIA PenTest+, Shodan and Censys are critical tools for Open Source Intelligence (OSINT) and passive reconnaissance. Unlike traditional search engines that index web content, these engines scan the entire internet to index metadata from connected devices, servers, and IoT systems. Their primary value lies in allowing penetration testers to map a target's attack surface without sending packets directly to the target network, thus avoiding early detection by Intrusion Detection Systems (IDS) or firewalls.
Shodan is often described as the search engine for hackers. It grabs 'banners'—metadata returned by a service upon connection—to identify operating systems, open ports, and service versions. Testers use specific filters such as 'org:' (to target a specific company), 'net:' (CIDR ranges), or 'vuln:' (to find devices with known CVEs). Shodan is particularly effective at discovering misconfigured devices, such as webcams with default passwords, exposed Industrial Control Systems (ICS), or unpatched servers running outdated software.
Censys operates similarly but provides deep visibility into TLS/SSL certificates and protocol handshakes. This is vital for discovering 'shadow IT' and hidden infrastructure. By analyzing certificate subject alternative names, a pen tester can find related subdomains or assets that belong to the organization but are not listed in public DNS records. Censys queries allow for granular searches based on HTTP response bodies and certificate issuers.
Together, these tools enable the enumeration phase by identifying potential entry points—such as exposed RDP ports (3389) or vulnerable web servers—allowing the tester to prioritize targets before commencing active scanning.
Mastering Shodan and Censys Usage for CompTIA PenTest+
Introduction to Specialized Search Engines
In the context of the CompTIA PenTest+ certification, Shodan and Censys represent essential tools for passive reconnaissance (Open Source Intelligence or OSINT). Unlike traditional search engines (like Google) that crawl web content, these engines scan the entire internet to index connected devices and systems.
Why It Is Important The primary importance of these tools lies in stealth. A penetration tester can map a target's external attack surface, identify open ports, and discover vulnerable services without sending a single packet to the target organization. This prevents early detection by Intrusion Detection Systems (IDS), Intrusion Prevention Systems (IPS), or Firewalls.
What They Are
Shodan: Often described as 'the search engine for the Internet of Things (IoT).' It aggregates information regarding servers, webcams, traffic lights, routers, and Industrial Control Systems (ICS/SCADA). It focuses heavily on banners—the metadata returned by a service when a connection is initiated.
Censys: A search engine that monitors the state of the internet. While similar to Shodan, Censys is highly regarded for its ability to analyze digital certificates (SSL/TLS) and track infrastructure hosts across different domains using cryptographic data.
How They Work Both platforms operate by continuously scanning the IPv4 address space. 1. Scanning: They attempt to connect to common ports (e.g., 80, 443, 22, 21, 3389) on random IP addresses. 2. Banner Grabbing: They capture the response headers (banners) provided by the services running on those ports (e.g., 'Apache 2.4.49' or 'Windows IIS 10.0'). 3. Indexing: The data is structured and searchable via filters such as IP, organization name, location, or specific software versions.
Exam Tips: Answering Questions on Shodan and Censys Usage
When facing PenTest+ exam questions, apply the following logic to select the correct answer:
Passive Requirement: If a scenario asks you to identify open ports, operating systems, or services without scanning the target or without touching the target's infrastructure, the answer is almost always Shodan or Censys. Contrast this with Nmap, which is active scanning.
IoT and SCADA/ICS: If the question specifically mentions finding exposed Internet of Things devices, webcams, or SCADA systems, Shodan is the primary keyword to look for.
Certificates and Trust Chains: If the objective involves analyzing SSL/TLS certificates to find related domains or subdomains, Censys is the most appropriate tool.
Vulnerability Verification: Questions may ask how to verify if a legacy server is visible to the public internet without alerting the SOC. Using Shodan to look up the organization's IP block is the correct methodology.
Filter Syntax: Be familiar with basic search operators. For example, searching `org:"Target Company"` in Shodan helps enumerate assets belonging to a specific client.