Shodan (Sentient Hyper-Optimised Data Access Network) is a search engine designed to map and gather information about internet-connected devices and systems. Shodan is sometimes referred to as a search engine for the internet of things (IoT). Applications of the software include market research, vulnerability analysis and penetration testing, as well as hacking.
Shodan makes it possible to detect devices that are connected to the internet at any given time, the locations of those devices and their current users. Such devices could be in almost any type of system, including business networks, surveillance cameras, industrial control systems (ICS) and smart homes. Shodan attempts to grab the system’s banner directly, gathering the data by way of the associated server’s ports. Banner grabbing is a key step for penetration testing as it helps identify vulnerable systems. Shodan also searches corresponding exploits in the search platform’s exploit section.
Shodan supports Boolean operators and provides filters to improve the efficiency of searching. The search engine provides 50 results for free and offers paid subscriptions for more extensive results.
John Matherly came up with the idea of searching Internet-connected devices in 2003 and launched Shodan in 2009. It quickly became apparent that hackers could use the tool to find vulnerable systems and that, furthermore, many systems all over the world were readily accessible and inadequately protected from hardware attacks, industrial espionage and sabotage.
Shodan is named for a character from a video game series called System Shock.