Twitter has introduced a "report tweet" option for users who are sent abusive messages following a campaign by a number of women who were targeted on the site.
Caroline Criado Perez said it was "great" that Twitter had taken a "first step" in dealing with harassment on the social media site, but said more needed to be done.
Ms Criado Perez, from north London, was one of a number of women who were subjected to a torrent of abuse by Twitter users last month.
She found herself at the centre of a public furore after she launched a campaign to have a woman's picture printed on a new banknote.
Walthamstow MP Stella Creasy also became involved after she offered support to the freelance journalist.
Classicist and television historian Professor Mary Beard, Guardian columnist Hadley Freeman, Independent columnist Grace Dent and Europe editor of Time magazine Catherine Mayer were also then targeted along with a number of other women.
They received bomb threats, while two of them were warned they would be raped by users of the site.
Ms Criado Perez said: "It's great that Twitter has listened.
"There are still issues: users have to agree for the report to be potentially shared with the harasser, and there are some boxes that could be auto-populated that aren't. But overall, this is a fantastic first step."
Kim Graham, who started the Change.org petition for Twitter to do more to protect its users, also welcomed the move.
She said: "I'm thrilled that Twitter has started making progress on this.
"Online bullying and harassment has been too common for too long, and this is a very welcome first step toward online safety for women.
"There are always improvements that can be made, but this proves that if we speak up together we can really have an impact."
More than 100,000 people signed the petition for Twitter to beef up its procedures for dealing with abuse.
The abusive messages saw at least three people arrested with Scotland Yard's e-crime unit examining allegations of abuse made by eight people on the site.
Twitter said the rollout of the in-Tweet report button had taken place ahead of schedule and it was already available for its iPhone users.
It means that users can report individual Tweets for abuse or spam on Android and on twitter.com, rather than having to go to its Help Centre to file an abuse report.