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tq-006-another-NXDOMAIN-domain-in-same-zone.md

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tq-006 Check another “NXDOMAIN” domain in same zone

When the suspected-to-be-censored domain returns the NXDOMAIN error from the resolver it is interesting to attempt a resolution of another domain that we know for sure to not exist. These two queries may result in different outcomes that may be a sign of network interference.

Examples

  • AS22047, VTR, Chile — “SOA? riseup.net.” sent to ISP’s resolver resulted in an NXDOMAIN reply with 0 answers and 0 authority records, while “SOA? riseup-5223-547-27075.net.” also was an NXDOMAIN with 0 answers, but had 1 authority records “a.gtld-servers.net. Nstld.verisign-grs.com ...” with valid Serial and other fields clearly distinguishing it as non-existent domain.