Whiskey, Weed, and Wukan on the World Wide Web: On Measuring Censors' Resources and Motivations

A snapshot from 6 April 2012 shows TOM-Skype had 1,130 censorship keywords and SinaUC had 1,490, with only 21 words in common — all high-frequency stock keywords (e.g., 'falun', 'Epoch Times'). This near-total divergence indicates each company independently compiled its own blacklist rather than distributing from a centralized government source.

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TOM-Skype's client-downloaded keyword blacklist was updated with current-event-specific terms (protest locations, individual names like Bo Xilai) while SinaUC's lists were not updated with current events and appeared more targeted at spam removal. This correlation between surveillance capability and more timely, politically specific keyword updates suggests censors prioritize maintaining current blacklists on clients that also perform message surveillance.

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Weibo's post-censorship system initially checks only for literal keyword strings, but after a user posts a literal blacklisted keyword the server switches to regex/wildcard matching for that user's subsequent posts — catching obfuscations like 'Fa-ccc-lun' that were not blocked before the trigger event. This per-user escalation of pattern matching means keyword obfuscation provides only one-shot protection.

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Weibo's search censorship is more aggressive than its post censorship: searching for a keyword returned no results in cases where posting the same keyword was not blocked. The authors hypothesize this asymmetry reflects resource constraints — post censorship requires processing longer, more varied content at high volume, while search censorship is cheaper to apply broadly.

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Bigram frequency analysis of Weibo around the December 2011 Wukan village protests (Figure 1) shows censorship of the keyword 'Wukan' was applied proactively before mainstream media coverage and lifted after the government announced a peaceful resolution on 21 December 2011 — demonstrating that censors operate on a news-cycle timescale and use temporary suppression to manage narrative rather than indefinitely blocking topics.

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