Developer Builds Passive Security Scanner Using Public Data to Avoid Legal Risk

A developer was commissioned to build a domain security scoring tool for a client's lead generation funnel, but quickly identified a legal problem with the standard approach. Active scanning methods such as port scanning can constitute unauthorized computer access under certain laws, even when no data is altered. To sidestep this liability entirely, the tool was redesigned to rely solely on data already collected by third-party services like Shodan, Censys, SSL Labs, and certificate transparency logs. These sources provide information on open ports, SSL configurations, and forgotten subdomains without sending a single packet to the target system. The result is a narrower but legally defensible tool suited for public-facing use cases where no prior authorization from the scanned domain's owner exists.