shodan

Shodan is a search engine for internet-connected devices and services. Launched in 2009 by John Matherly, it catalogs information about devices that are directly reachable over the internet, including web servers, routers, cameras, industrial control systems, and cloud services. Unlike traditional web search engines, Shodan focuses on metadata and banners exposed by services rather than indexing linked webpages.

Data collection and indexing: Shodan uses automated crawlers to scan IP addresses and ports across the internet. For each observable service, it captures banners, version numbers, and other metadata provided by the software or device. The resulting records typically include the IP address, port, host name, organization, approximate geographic location, and clues about the device type and software. Users can query the index with filters such as country, city, organization, operating system, port, or specific banner content.

Uses and impact: Shodan is widely used by security professionals for asset discovery, incident response, and vulnerability assessment. It helps administrators identify exposed devices, monitor for misconfigurations, and track the exposure of critical infrastructure. Researchers examine trends in device security and software versions. The tool has also drawn concern for potentially facilitating cybersecurity attacks by simplifying the location of internet-facing devices with known vulnerabilities.

Access and limitations: Shodan offers free access with basic search and paid plans for API access and higher usage limits. The coverage depends on what is publicly reachable and detectable; not all devices are discoverable, and banners may be outdated or misleading. It also raises ethical and legal considerations regarding scanning and indexing of networked devices.