behind the internet censorship wall
Digital contents sometimes tend to be censored by governments all around the world especially in the undemocratic countries like Iran and China
Everyone knows that netizens in Iran are under oppression. Digital contents sometimes tend to be censored by governments all around the world especially in the undemocratic countries like Iran and China, censorship reason it might not be clear but mostly is because of religious grounds, or business reasons or might ideologically unpleasant to those in the power of censoring, what so ever the page would be blocked.
In this blog post, I summarized ten years of experience in dealing with online censorship methods and would describe how a government or even companies might block a page. All of these methods are being used in Iran, Iran’s government has been practicing Internet censorship for more than a decade.
Preventing IP addresses:
most of the time internet service providers, or more specifically government firewalls tend to limit the IP address of websites, for instance, might belong to twitter or Facebook, in this case, firewalls ban the IPs associated with those pages, it is not clear How long IPs are ban in those firewalls. It seems that firewalls always resolving those IPs and block them before User can get reach them, using proxy might work in some places but in countries like Iran and China would not do the best option always in VPNs like OpenVPN sometimes shadowsocks works but not always
Broadband speed limitations:
In Iran the bandwidth of home users limited to 128 kb/s. It is believed that this limitation is imposed to hinder access to multimedia content such as streaming audio and video. Researchers, faculty members, and university students are exempt from this limitation upon providing the appropriate documentation.
DNS queries for some sites respond with a fake local IP address for example a local network up which in Iran is (10.10.34.34) that acts as a black hole.
HTTP host and keyword filtering:
The Government block access to certain prohibited sites by manipulating connections based on the HTTP Host header. Access to URLs containing specific keywords is also blocked. The list of prohibited keywords originally contained tems which is been using in search on restricted pages.
Connection throttling: In addition to these techniques, Iran has been observed to deploy connection throttling, particularly during times of political and economic unrest. This has sometimes taken the form of throttling speeds to specific sites or protocols and sometimes complete throttling of all traffic. Certain protocols, including HTTPS, SSH and VPN tunnels, have also been reported to be blocked or throttled at times.