Since the evening of August 26, Russian TSPU (technical means of countering threats) have started redirecting open DNS queries addressed to Google and Cloudflare public DNS servers toward the National System of Domain Names (NSDI). The change affects users of multiple Russian internet providers and coincides with ongoing implementation of content filtering systems required by Russian legislation.
When a standard UDP DNS query is sent to addresses such as 8.8.8.8 or 1.1.1.1 for domains including YouTube and RuTracker, the response returned is NXDOMAIN, indicating that the domain does not exist. In contrast, identical queries sent over TCP successfully reach the original servers and obtain genuine IP addresses.
Further traffic analysis by Habr user angry_agent showed that packets with a deliberately low TTL value elicited ICMP TTL Exceeded messages containing the IP address 195.208.5.1, which belongs to NSDI. The same behavior was not observed with arbitrary UDP packets, confirming that the system specifically inspects DNS traffic.
According to the researcher, TSPU devices recognize open DNS queries and perform a directed DNAT operation, transparently altering the destination address so that the packet is delivered to an NSDI server. The national resolver then decides what response to return to the user. From the perspective of the network operator, the query appears to have been sent directly to NSDI rather than to a foreign resolver.
The mechanism is not flawless. When several identical queries are transmitted rapidly, the first request receives an NXDOMAIN response while subsequent requests reach Google and return correct addresses. Redirection also does not occur for every public DNS server tested.
No official statement confirming the new redirection technique has been issued by Russian authorities or network operators. The conclusions are based solely on the experiments of a single researcher. The development follows reports from users of several Russian providers who experienced difficulties accessing protected DNS services operated by Google and Cloudflare.

