Messages identified as abusive will not appear on notification timelines, thanks to a new filtering system designed to prevent harassment from being seen by its targets.

Twitter is also tightening its terms of service, banning indirect threats and formalizing its suspension system.

The changes are among the first to show up since CEO Dick Costolo said he was “frankly ashamed of how poorly we’ve dealt with this issue” in a recent interview.

The criterion for detecting abusive messages involve new accounts and the use of language similar to earlier messages flagged as abusive. Such tweets will not be removed–they will simply be blocked automatically from view.

“This feature takes into account a wide range of signals and context that frequently correlates with abuse including the age of the account itself, and the similarity of a Tweet to other content that our safety team has in the past independently determined to be abusive. It will not affect your ability to see content that you’ve explicitly sought out, such as Tweets from accounts you follow, but instead is designed to help us limit the potential harm of abusive content,” Shreyas Doshi, Twitter’s head of product management, wrote in an official blog post.

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