[liberationtech] Measuring the Deployment of Network Censorship Filters at Global Scale

[Yosem Companys]

 Content  filtering  technologies  are  often  used  for Internet
censorship,  but  even  as  these  technologies  have  become cheaper  and
 easier to  deploy,  the  censorship  measurement  community lacks a
systematic approach to monitor their proliferation. Past research has
focused on a handful of specific filtering technologies,  each  of  which
 required  cumbersome  manual  detective work  to  identify.  Researchers
 and  policymakers  require  a  more comprehensive  picture  of  the  state
 and  evolution  of  censorship based  on  content  filtering  to
establish  effective  policies that  protect  Internet  freedom. In this
work, we present FilterMap, a novel framework that can scalably monitor
content filtering technologies based on their blockpages. FilterMap first
compiles in-network and new remote censorship  measurement  techniques  to
 gather  blockpages  from filter  deployments.  We  then  show  how  the
 observed  blockpages can be clustered, generating signatures for
longitudinal tracking. FilterMap outputs a map of regions of address space
in which the same  blockpages  appear  (corresponding  to  filter
 deployments), and  each  unique  blockpage  is  manually  verified  to
 avoid  false positives. By  collecting  and  analyzing  more  than  379
 million  measurements  from  45,000  vantage  points  against  more  than
 18,000sensitive test domains, we can identify filter deployments
associated   with   90   vendors   and   actors   and   observe   filtering
in   103   countries.   We   detect   the   use   of   commercial
filtering technologies  for  censorship  in  36  out  of  48  countries
 labeled  as‘Not  Free’  or  ‘Partly  Free’  by  the  Freedom  House
 “Freedom on  the  Net”  report  [26].  The  unrestricted  transfer  of
content filtering  technologies  have  led  to  high  availability,  low
 cost,  and highly  effective  filtering  techniques  becoming  easier  to
deploy and harder to circumvent. Identifying these filtering deployments
highlights  policy  and  corporate  social  responsibility  issues,  and
adds accountability to filter manufacturers. Our continued publication of
FilterMap data will help the international community track the scope, scale
and evolution of content-based censorship.

https://www.ndss-symposium.org/wp-content/uploads/2020/02/23099-paper.pdf
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