Knocking on IPs: Identifying HTTPS Websites for Zero-Rated Traffic

Table 1

Summary of website identification methods for zero-rating.

Method	HTTPS	Support	In-band	ESNI and DoH	Free-riding I	Free-riding II	Open set	Known usages
Non-HTTPS			✓			✓	✓	Various ISPs [8, 9]
SNI	✓	Post-2006 clients	✓			≈	✓	Various ISPs, censorship [40]
Whitelisting IPs	✓	CP	✓	✓	✓	✓		Wikipedia zero [3], censorship [40]
DNS	✓		✓			✓	✓	Facebook zero [37], censorship [40]
Verify SNI by DNS	✓					✓	✓	Cisco patent [39]
Network cookies	✓	CP	✓	✓	?	?	?	?
WPF	✓		✓	✓		≈		Censorship [41]
Self-signed	✓	Client	✓	✓		✓	✓	Enterprise and surveillance governments [42, 43]
Reverse DNS	✓	CP		✓	≈	✓	≈	Antispoofing, OSINT tools (e.g., Maltego)
Open-Knock	✓			✓	✓	≈	✓

“≈” indicates a dependency on the specific zero-rating implementation used.