Anti-porn filters stop Dominic Cummings trending on Twitter

Name of PM’s aide is blocked, which has led to variety of misspelt hashtags

Twitter’s anti-porn filters have blocked Dominic Cummings’ name from its list of trending topics despite Boris Johnson’s chief adviser dominating British political news for almost a week, the Guardian can reveal.

As a result of the filtering, trending topics over the past five days have instead included a variety of misspellings of his name, including #cummnings, #dominiccummigs and #sackcummimgs, as well as his first name on its own, the hashtag #sackdom, and the place names Durham, County Durham and Barnard Castle.

The filter also affects suggested hashtags, meaning users who tried to type #dominiccummings were instead presented with one of the misspelled variations to auto-complete, helping them trend instead.

This sort of accidental filtering has gained a name in computer science: the Scunthorpe problem, so-called because of the Lincolnshire town’s regular issues with such censorship.

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Bizarrely, the shortened hashtag #cumgate has also trended, since the first syllable is not included in Twitter’s filter list, apparently in an attempt to avoid the Scunthorpe problem applying too broadly – for instance, by blocking words such as “scum”, “cumbersome” or “cumulative”.

Although Twitter does not publish the contents of the word filter list, users can check whether a particular term is blocked from trending by searching for it. By default, the site blocks all photo and video results from search terms it believes may contain sensitive content, meaning a media search for “porn” or “Cummings” will, unless the search filters are turned off, return zero results.

Twitter declined to comment on the filtering. The company’s opaque trending algorithms have regularly led to accusations of interference, as users conclude that the absence of a particular topic is a sign of malicious intent, but the answer is rarely as straightforward as it is in this case.

Typically, topics trend due to marked deviations from a baseline of interest. That means it can be hard for a topic to trend if it is always under discussion – explaining why the company’s products do not constantly report trends for K-pop and Donald Trump.

That requirement also ensures continuing novelty in trending topics by raising the threshold for each successive period, so a topic that suddenly becomes the centre of attention will not monopolise the list for weeks or months.

Unfortunately for Cummings, the regular revelations – and inventive misspellings – mean new trending topics have arrived each day, with Saturday’s #sackcummimgs giving way to Tuesday’s “Barnard Castle Eye Test” and Wednesday’s “Dim and Dom”.