  Over the years, the Internet has democratized the flow of information.
Unfortunately, in parallel, authoritarian regimes and other entities (such as
ISPs) for their vested interests have curtailed this flow by partially or fully
censoring the web. The policy, mechanism, and extent of this censorship varies
from country to country.
  We present the first study of the cause, effect, and mechanism of web
censorship in Pakistan. Specifically, we use a publicly available list of
blocked websites and check their accessibility from multiple networks within
the country. Our results indicate that the censorship mechanism varies across
websites: some are blocked at the DNS level while others at the HTTP level.
Interestingly, the government shifted to a centralized, Internet exchange level
censorship system during the course of our study, enabling our findings to
compare two generations of blocking systems. Furthermore, we report the outcome
of a controlled survey to ascertain the mechanisms that are being actively
employed by people to circumvent censorship. Finally, we discuss some simple
but surprisingly unexplored methods of bypassing restrictions.
