This report presents the largest study of DNS censorship in India till date, both in terms of test list coverage as well as the size of blocklist produced. The study tested 294 million domains across six ISPs representing approximately 82% of internet subscribers in the country, identifying 43,083 blocked apex domains.
The compiled blocklist produced by this study represents a sixfold increase over the previous largest censorship study, though it is still likely a lower bound, owing to methodological and protocol limitations. The analysis revealed a misconfigured blocking rule causing significant overblocking, where a major ISP blocked an entire gTLD (.yokohama).
Blocking of domains across ISPs extended aggressively to services and platforms in categories including business, hosting, research, and communication. Additionally, a state-owned PSU ISP’s consumer blocklist is hypothesized by the author to include domains supposed to be blocked only within government offices. The scale of this study allowed for the production of evidence of significant overblocking which would otherwise not be captured. This is further emphasized when considering that only 9,363 (21.73%) blocked domains had a rank in the Tranco list. DNS filtering continues to remain a popular censorship technique for both small and large Indian ISPs. This will likely remain the case, unless there are major changes in the state’s censorship policies.
Read the full report here: https://dnsblocks.in/assets/report.pdf