The Tor Project's community team noticed that OONI's Tor test, which tests access to Tor's directory authorities and Tor Browser's default obfs4 bridges, showed evidence of blocking in a small number of ASes in Russia since 2021-12-01. The same ASes, before that date, did not show signs of blocking. Further analysis shows that the blocking is mostly concentrated in Moscow.
@ValdikSS did manual testing and found that it is not only plain Tor and default obfs4 bridges that are blocked, but all default pluggable transports present in Tor Browser:
- Plain Tor (no obfuscation) – connection timeout (no response to SYN).
- Default obfs4 bridges – connection timeout (no response to SYN).
- meek-azure – connection timeout (in some cases as if the IP addresses of ajax.aspnetcdn.com were blocked, in at least one other case looking like SNI filtering of ajax.aspnetcdn.com).
- Snowflake – connection breaks after several KB are transfered.
- obfs4 bridges from Moat – returns bridge IP addresses, but none of the three bridges worked.
However, obfs4 bridges from bridges.torproject.org, obfs4 bridges from bridges@torproject.org, and a private obfs4 bridge all worked.
@ValdikSS ran additional diagnostics for blocking of ajax.aspnetcdn.com specifically (used in meek-azure).
From the RIPE Atlas measurement map page, we can see that the blocking of ajax.aspnetcdn.com correlates with geography. 16 of the failed probes are in Moscow, and 1 is in Saint Petersburg:
The 466 non-failed probes are located all over Russia, including in Moscow and Saint Petersburg:
The Tor Project's community team noticed that OONI's Tor test, which tests access to Tor's directory authorities and Tor Browser's default obfs4 bridges, showed evidence of blocking in a small number of ASes in Russia since 2021-12-01. The same ASes, before that date, did not show signs of blocking. Further analysis shows that the blocking is mostly concentrated in Moscow.
@ValdikSS did manual testing and found that it is not only plain Tor and default obfs4 bridges that are blocked, but all default pluggable transports present in Tor Browser:
However, obfs4 bridges from bridges.torproject.org, obfs4 bridges from bridges@torproject.org, and a private obfs4 bridge all worked.
@ValdikSS ran additional diagnostics for blocking of ajax.aspnetcdn.com specifically (used in meek-azure).
From the RIPE Atlas measurement map page, we can see that the blocking of ajax.aspnetcdn.com correlates with geography. 16 of the failed probes are in Moscow, and 1 is in Saint Petersburg:
The 466 non-failed probes are located all over Russia, including in Moscow and Saint Petersburg:
