The anonymising service Tor has seen a huge surge in use this month with the number of daily directly connecting users shooting up from a fairly consistent average of 550,000 over the last year to over 1,200,000 in August.
The number beats the network's previous peak in January 2012 by a long way, when it recorded around 975,000 daily users.
With privacy concerns growing in the US and UK, the Register reports that at the start of August around 90,000 Americans and 16,000 from the UK were connecting to Tor daily, but that the figure has now grown to around 150,000 daily users in the US and 35,000 in the UK.
India too saw a large increase in Tor usage as the average number of daily users leapt from 7,500 to 32,000 and China registered around 400 Tor users - significant given the country's internet controls via what's often referred to as the 'Great Firewall of China'.
Even Tor's Roger Dingledine is not sure what's going on.
Dingledine said "It's easy to speculate" as to what could be behind this surge in usage of Tor which anonymises internet traffic through a complicated network of connections and redistribution points around the world.
Recent revelations from Edward Snowden about the NSA's PRISM program being used to track global internet activity is an obvious starting point when looking for causes.
Other significant events that may have led to an increase in Tor usage during August include the sudden and voluntary closing of secure email providers Lavabit, used by Snowden, and Silent Circle on 8 August.
Lavabit owner Ladar Levison closed his service down, saying that a government investigation would force him to "become complicit in crimes against the American people."
In an interview with The Guardian Levison said, "We are entering a time of state-sponsored intrusion into our privacy that we haven't seen since the McCarthy era. And it's on a much broader scale."
Then, on 10 August, the Pirate Bay file-sharing site released Pirate Browser - a web browser that uses Tor to aid users in circumventing government censorship of specific sites such as torrent networks and other file-sharing sites. (Note: readers concerned with their privacy and considering the Pirate Browser should understand that, unlike Tor, it does not anonymise its users.)
Later in the month the partner of Glenn Greenwald, the journalist who has broken a series of stories about Edward Snowden, was detained for nine hours at Heathrow airport. The upturn in Tor usage can be clearly seen a couple of days after David Miranda's arrest on 18 August.
But there is something a bit odd about all of this. The chart is actually remarkable for how much it doesn't change throughout these seismic events.
Usage is determinedly unchanging despite a multitude of reasons for it to increase and then suddenly, inexplicably, it doubles from a year-long plateau in the space of a week.
The folk on the tor-talk mailing list are suspicious too. The last exchange on the subject reflects a feeling among some that the growth is unnatural:
grarpamp: Too big a double in under a week for me to believe it's natural growth ... I'd guess it got included in some app. A botnet fits perfect ... Or its some sort of analysis/attack/flood against the dirs.
Paul Syverson: Or somebody's research experiment gone awry, or behaving predictably but that they didn't think a concern worth mentioning, or...
Malicious stuff happens, but most of the time these things are incompetence or similar rather than malicious intent.
Whether it's a botnet, a research experiment or something else altogether, the jury is out on the cause of the increase in Tor usage.
What's your theory? Let us know in the comments below.