Detect outgoing port blocking with nmap and

This post will describe how to detect if your network is blocking outgoing ports. In this test, we’ll be using nmap and the fine website

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Detecting Censorship or ISP Network Tampering with OONI

This article will introduce a tool to detect censorship or network tampering using the Open Observatory of Network Interference (OONI) android app, which is part of the Tor Project.

The OONI project’s mission is to collect data on network providers to determine where the Internet is free and where it’s being manipulated. For example, the OONI Explorer displays a world map of such data.

On the OONI explorer, you can drill-down on the world map into a specific country to get a list of websites that were detected as being blocked from within that country.

For example, when I looked at the history of OONI probe runs within the US, I saw a list of the usual suspects: gambling sites, pornography sites, torrenting sites, etc. More surprising (at least to me) was the number of pastebin sites that were banned. And, despicably, there was a network in the US blocking The Internet Archive

When I looked at the data from scans within another great “free country” = India, I saw a lot of cherry-picked censorship on facebook and news articles as it relates to the 2017 genocide of Rohingya Refugees in Burma and various muslim/hindu conflicts.

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Using uBlock Origin to Whitelist

As some mega websites deploy APIs that are used nearly ubiquitously on most of the Internet’s websites (I’m looking at you Facebook & Google), I’ve begun to compartmentalize my browsers to “jail” specific website usage to a single, sandboxed browser (profile). This is sometimes referred to as a Single Site Browser (SSB).

Besides making sure that your SSB is isolated in that it cannot access your regular browser’s data (a configuration I plan to document in the future), it’s essential to block all network traffic from/to your SSB and all websites, except a whitelist. Unfortunately, getting block-all-then-whitelist functionality in uBlock Origin was annoyingly not documented, so I decided to publish it.

If you want uBlock Origin to block all traffic, add the following line to the textbox in your “My filters” tab of uBlock’s Dashboard.

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pycurl through Tor without leaking DNS lookups

This article describes the correct way to use pycurl over Tor, such that both DNS lookup data and HTTP(S) traffic is sent through Tor’s SOCKS5 proxy.

If you google “pycurl tor”, one of the first results is a stackoverflow post that describes how to configure pycurl using the pycurl.PROXYTYPE_SOCKS5 setting. Indeed, even the tutorial To Russia With Love on the Tor Project’s Official Website describes how to pass pycurl through Tor using the pycurl.PROXYTYPE_SOCKS5 setting.

However, using pycurl.PROXYTYPE_SOCKS5 will leak DNS queries associated with your HTTP requests outside of the Tor network! Instead you should use pycurl.PROXYTYPE_SOCKS5_HOSTNAME.

The –socks5-hostname argument was added to libcurl v7.26.0. The pycurl.PROXYTYPE_SOCKS5_HOSTNAME argument wasn’t added to pycurl until pycurl v7.19.5.1, which (at the time of writing) was less than 2 months ago!

This article will describe how to install pycurl v7.19.5.1 onto the latest version of TAILS at the time of writing, which is TAILS v1.2.3.

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