Search Mailing List Archives

Limit search to: Subject & Body Subject Author
Sort by: Reverse Sort
Limit to: All This Week Last Week This Month Last Month
Select Date Range     through    

[liberationtech] Many VPNs and Psiphon are currently blocked in Iran right now

Adam Pritchard a.pritchard at
Tue Feb 25 12:41:09 PST 2014

I thought I should chime in with some info about Psiphon's recent blockage
in Iran...

On February 14, we had about 840K Android + 620K Windows unique users (on
that day; the total for the preceding week was about 3m, as Collin said).
This is almost the high water mark for us.

On February 15, we were down to 500K Android users + 400K Windows users. On
February 16, we were down to 150K Android users + 180K Windows users.
Unsurprisingly, we were also getting hammered with user feedback (about 10x
normal) and email auto-responder requests (at least 5x normal) -- tens of
thousands of both.

So, yeah, Iran dropped the hammer on us.

There's a very good chance that this is related to the anniversary of the
Iranian Revolution -- which is February 11, but there are other dates in
the vicinity (e.g., the house arrests of the opposition leaders was Feb

The Fars news agency (which is believed to be a tool of Iran's
Revolutionary Guard Corps) published an article (<>) on February 18
which said: "A reliable source in contact with Fars news agency, talked
about blocking of Psiphon since three days ago. He also talked about
blocking of Chrome extension "Zenmate" and also mentioned the plan to block
8 other circumvention tools." (Thanks to Fereidoon at ASL19 for the
translation and Revolution info.)

Our (and Collin's) investigation results have been difficult to interpret
(and/or get solid knowledge from), but we've seen some of our IPs that are
blocked across all ports, and some that are blocked just on the ports we
use for SSH/OSSH/VPN. (It might be that it varies by ISP.) We suspect that
the censors might have been collecting our IPs for a while and then blocked
a bunch all at once. New servers/IPs that we've created since the blocking
seem to work, so the blocking is probably not DPI-based. However, many new
IPs are still getting blocked faster than normal, so it seems that Iran's
censors are still being very aggressive.

As of yesterday we've managed to recover a bit to 280K Android users + 250K
Windows users. We are pumping out new servers and working on new ideas for
dealing with new blockage events (and maybe this one, if it keeps going

...And that's where we are now. If anyone has any questions, ideas, info,
etc., please let us know.


I also feel I should comment on a couple of things that Nathan said:

> If Tor is harder to block (which it is)
> That is the reason I promote Tor. ... i see it as something you can trust
and rely upon that wont leave user out to dry the minute the govt filters
their IP.

I would advise against getting too comfortable/confident/hubristic. Tor has
2000 bridges and we were up to over a 1000 IPs. Tor has a bridge discovery
mechanism and Psiphon has a server discovery mechanism. Tor has an
obfuscated protocol and Psiphon has an obfuscated protocol. There are
enormous differences, of course, but if Tor gets to a million Iranian users
and then the censors decide specifically and publicly to target it... One
might not want to suggest that one is unblockable.

Adam Pritchard
Psiphon Inc.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>

More information about the liberationtech mailing list