How to Use Shodan 2026 — The Hacker’s Search Engine Complete Guide

This guide explains Shodan, a search engine indexing over 15 billion internet-facing services and their banners, and demonstrates how to use it for passive reconnaissance in bug bounty and penetration testing. Unlike Google which indexes web pages, Shodan indexes service banners—raw responses from SSH servers, databases, cameras, and industrial control systems—revealing exposed attack surface that web search cannot find. The article provides practical techniques for querying exposed services, building automated reconnaissance workflows, and continuously monitoring target infrastructure, while emphasizing that searching is legal but accessing discovered devices without authorization remains illegal.

• How Shodan fundamentally differs from GoogleShodan continuously scans all 4.3 billion IPv4 addresses on common and uncommon ports, recording service banners—the raw response a network service sends before credentials are required, such as SSH version strings, HTTP server headers, database announcements, and industrial control system model numbers. Google indexes web page content and meta data but does not index these raw service responses. When searching Shodan for MongoDB, you access the banners of every internet-facing MongoDB instance ever observed, including those without authentication, whereas Google cannot find these services at
• Core filters for targeted attack surface discoveryThe org filter (org:"Company Name") finds all indexed assets belonging to an organization, the hostname filter (hostname:domain.com) correlates Shodan results against DNS enumeration to identify unexpected IPs, and the SSL certificate filter (ssl.cert.subject.cn:domain.com) reveals infrastructure covered by wildcard certificates that DNS enumeration misses. Port filters (port:27017 for MongoDB, port:6379 for Redis) combined with negative filters (-"authentication") isolate unauthenticated services. These filters can be combined to create structured recon workflows that map complete attack surf
• Shodan dorks combine multiple filters for efficiencyDorks are pre-built multi-filter queries targeting specific exposed service types: http.title:"Admin" http.status:200 org:"Target" finds exposed admin panels, http.title:"Dashboard [Jenkins]" port:8080 finds Jenkins CI/CD instances, and port:27017 "MongoDB" -"authentication" finds unauthenticated databases. These queries allow security researchers to find high-value targets systematically rather than through random exploration, with repositories of hundreds of dorks available covering specific device types and vulnerability patterns.
• ASN-based reconnaissance for complete coverageFinding a company's Autonomous System Number (ASN) via bgp.he.net or Shodan search results enables searching all IP ranges owned by that company, including ranges not obviously linked to the company name in WHOIS records. The query asn:AS12345 with optional service filters (asn:AS12345 port:8443) covers infrastructure that the org filter might miss due to naming variations or subsidiary structures. The Shodan CLI command "shodan download" can retrieve all IPs under an ASN into a file for offline analysis.
• CLI automation integrates Shodan into recon pipelinesThe Shodan Python library installed via pip can be initialized with an API key and scripted for automated queries. The shodan host command quickly reveals what Shodan knows about any IP—open ports, software versions, historical data. Results can be piped through standard Unix tools (jq, awk, grep) to extract specific fields, filter by criteria, and feed into other reconnaissance tools. Free accounts allow 100 API queries per month; the CLI works on Kali Linux and other systems with Python.
• Certificate indexing reveals hidden infrastructureSSL certificate filters (ssl.cert.subject.cn:target.com) often reveal subdomains and infrastructure that neither DNS enumeration nor web search discovers because certificates are issued for infrastructure before or instead of DNS records being created. Censys has particularly strong TLS/SSL certificate indexing through its parsed.names search and is complementary to Shodan for this purpose. Cross-referencing Shodan IPs against subdomain enumeration results identifies shadow IT and forgotten assets not appearing in DNS.
• Alerts enable continuous discovery of new assetsShodan Alerts is a paid feature notifying users when new devices or services appear in Shodan's index for specified IP ranges or networks. For bug bounty targets, alerts on company IP ranges mean notification before other hunters discover newly internet-facing assets, which are often freshly deployed and less hardened. The free tier allows monitoring up to 16 IPs; paid tiers expand this to full netblock monitoring. Alerts are configured through the Monitor section of shodan.io by entering target IP ranges and selecting which port and service changes trigger notifications.
• Complementary tools provide complete coverageCensys and FOFA index overlapping but distinct subsets of the internet, sometimes surfacing infrastructure Shodan misses. Censys excels at certificate discovery with 250 free queries monthly and free Academic access for students. FOFA is a Chinese intelligence platform with particularly strong APAC region indexing that Shodan under-represents. Running the same org and hostname queries across all three platforms, then merging unique IP results and feeding them into Nmap for verification, produces a near-complete internet-facing asset inventory.

Bottom line: Shodan is a passive reconnaissance tool that reveals exposed internet-facing services through service banner indexing, and systematic use of org filters, hostname filters, SSL certificate queries, and automated CLI workflows can discover complete attack surfaces in minutes—but users must remember that searching Shodan is legal while accessing any discovered device without authorization remains illegal regardless of how it was found. The most valuable real-world application is combining Shodan's