ZMap: Fast Internet-wide Scanning and its Security Applications

High-speed Internet-wide scanning enables a censor or attacker to locate every publicly reachable host vulnerable to a newly disclosed flaw within hours of disclosure; in a concrete example, 3.4 million UPnP-vulnerable devices were identified in under 2 hours — faster than network operators could apply patches — with a 150-SLOC probe module written in approximately 4 hours.

§4.3 detection active-probingmeasurement-platform generic

Obfsproxy (predecessor to obfs4) listens on randomized ports as an explicit defense against discovery by comprehensive Internet-wide scanning, because an adversary must scan all 65,535 ports to locate bridges rather than a single known port — multiplying scan cost by roughly 65,000× relative to a single-port sweep.

§4.4 defense active-probingport-blocking

Comprehensive Internet-wide scanning enables cross-IP tracking of users and devices by correlating stable cryptographic identifiers — TLS certificates or SSH host keys presented by home routers and cable modems — with public geolocation data across DHCP lease changes, defeating the anonymity assumption behind dynamic IP addresses.

§4.6 detection tls-fingerprintmeasurement-platform generic

By scanning ports 443 and 9001 and fingerprinting responses with Tor's TLS v1 cipher-suite handshake pattern, ZMap identified 79–86% of all allocated Tor bridge fingerprints in a single scan, demonstrating that bridges whose protocol is distinguishable are largely discoverable through comprehensive Internet-wide scanning even though their addresses are not publicly listed.

§4.4 detection active-probingtls-fingerprintmeasurement-platform generic

ZMap completes a single-port scan of the entire public IPv4 address space in under 45 minutes from a commodity machine with a gigabit Ethernet connection, over 1,300 times faster than the most aggressive Nmap configuration. A single-probe scan achieves approximately 97.9% coverage of live hosts, rising to 98.8% with two probes and 99.4% with three probes.

§3, §3.2, §3.4, Table 1 evaluation measurement-platform