On Shodan, what specific part of a device's public listing tells you its software name and version, hinting at known weaknesses?

The specific part of a device's public listing on Shodan that reveals its software name and version, hinting at known weaknesses, is primarily the banner information. A banner is the initial text response sent by a service running on an exposed port when Shodan connects to it. For example, when Shodan connects to a web server on port 80, the server might send an HTTP header containing a 'Server' field like 'Apache/2.4.41 (Ubuntu)' or 'nginx/1.18.0'. Similarly, an SSH server on port 22 might return 'SSH-2.0-OpenSSH_8.2p1 Ubuntu-4ubuntu0.3', and an FTP server on port 21 might respond with '220 ProFTPD 1.3.5e Server'. These banner responses explicitly state the software name and its exact version number. This precise version information is crucial because it allows users to cross-reference the software and version against public vulnerability databases. Many known weaknesses, or vulnerabilities, are specific to particular software versions and are often assigned a Common Vulnerabilities and Exposures (CVE) identifier. By identifying a specific version from the banner, one can search for corresponding CVEs that describe known security flaws, which could include exploits for unauthorized access or denial-of-service attacks. Shodan compiles and displays these raw banner responses as a core part of each device's detailed public listing, making the software and version details readily available for analysis.