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[liberationtech] Tracking surveillance and censorship in TOM-Skype and Sina UC

Masashi Nishihata masashi at
Tue Jul 2 07:26:24 PDT 2013

Dear LibTech,

The Citizen Lab and Prof. Jedidiah Crandall and Jeffrey Knockel of the
Department of Computer Science at the University of New Mexico are proud
to announce the release of our paper “Chat Program Censorship and
Surveillance in China: Tracking TOM-Skype and Sina UC” in the July 2013
edition of First Monday.

In this study we examine the implementation of censorship and
surveillance in two IM clients maintained by two different Chinese
companies. For a period of more than a year and a half, we downloaded
and decrypted the censorship and surveillance keyword lists used by the
client software of two IM programs used in China: TOM-Skype and Sina UC.

We obtained the keyword list URLs and encryption keys by reverse
engineering the software binaries of the clients. In the TOM-Skype
client, keyword lists are used to trigger censorship and/or surveillance
of user chats, while in Sina UC the keyword lists trigger only
censorship. This data affords a rare opportunity to analyze the contents
of, and updates to, complete and unbiased keyword lists used for both
censorship and surveillance.

This dataset represents the largest unbiased surveillance and censorship
keyword list ever available to the research community. The data offers
insights into China’s information control regime but also raises further
questions on how industry enforcement works in practice in China, the
social and political implications of these IM clients’ censorship and
surveillance operations, and how surveillance and censorship features of
these IM clients compare to those of other Internet services in China.

All of the data and visualizations of this study are available on a
dedicated website that is designed to aid the
analysis of this unique dataset and encourage researchers to further
explore the data and open questions emerging from it.

*Key Findings*

*Variance in Keyword Lists Between Clients*

Comparing the keyword lists of the two clients reveals very little
overlap. The full dataset of 88 combined lists contains 4,256 unique
keywords, of which only 138 terms (3.2%) were shared in common between
TOM-Skype and Sina UC. This lack of overlap suggests that no common
keyword list was provided to these companies by government authorities.
These inconsistencies suggest that companies may be given general
guidelines from authorities on what types of content to target, but have
some degree of flexibility on how to implement these directives.

Explore the keywords here:

*Highly targeted and overly broad keyword content*

Targeted keywords include highly specific information such as
instructions and locations related to Jasmine rallies, names of
dissidents, and neologisms used by Chinese users to discuss sensitive
issues. The targeted nature of these keywords raises concerns regarding
the ultimate impact of censorship and surveillance on users discussing
such sensitive issues and social mobilizations. Other keywords were very
generic (e.g. Chinese people” “华人”, and “Internet” “互联 网”), which
raises implications of overly broad surveillance of users.

Explore the keywords here:

*Keyword list changes affecting censorship and surveillance functions*

Significant changes to keyword lists in both clients affected the
implementation of censorship and surveillance functions. The most recent
update to the censorship lists for the latest versions of TOM-Skype
versions reduced these lists to a single keyword, effectively
eliminating censorship on these versions of the client. However, these
versions still maintain active surveillance-only lists and earlier
versions of the client (3.6–4.2) retain active censorship lists, which
means that the latest versions of TOM-Skype analyzed in our study focus
on keyword surveillance.

Similarly, on September 17, 2012, four of the five Sina UC lists were
reduced to a single keyword. The remaining keyword list is used to
censor the username a user may select, meaning that censorship of
incoming and outgoing messages appears to be effectively eliminated in
Sina UC. It is possible, however, that Sina UC has implemented
surveillance features on the server side that we are unable to detect
with our reverse engineering methods.

Explore the list changes here:

Surveillance and censorship in reaction to sensitive events

We identified current events referenced in the dataset that occurred
within our data collection time frame and correlated keyword list
updates with the timeline of the events. Across the selected cases we
observed inconsistent patterns. In some cases keyword updates were
implemented within a single day of a sensitive event. In other cases,
updates were applied weeks or months after the event took place,
potentially indicating the censors only responded after an issue
developed sufficient political salience.

Explore correlations to current events here:

Masashi Nishihata
Research Manager, Citizen Lab
Munk School of Global Affairs
University of Toronto

Phone: (416) 946-8903
pgp key:

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