Being linked to malicious content, even if unintended, might have damaged that credibility.
Mr. Prosser said Twitter had taken an active role in combating the biggest sources of malicious content.
Five years ago, Google started a "Safe Browsing" initiative to track down malicious content across the Web.
One venture capitalist, writing on the tech blog Venture Beat, imagined deploying artificial intelligence as a "media cop," protecting users from malicious content.
The change was the latest in a series of attempts by YouTube to improve the friendliness of the platform to advertisers by cutting down on malicious content.
According to Cisco's 2013 annual security report, "online advertisements are 182 times more likely to deliver malicious content than pornographic sites".
Mr. Prosser said Twitter had manual and automatic controls in place to identify malicious content and fake accounts, but acknowledged that the practice was more art than science.
The spectacle of Welch's attack and arrest fuelled further concerns over fake news and malicious content, which had already gripped commentators in the latter days of the Presidential election.
A letter obtained by the Guardian from SMSGlobal to the Dubai telecommunications company DU following the April 2015 breach said text messages had been received with "malicious content" arising from a number of accounts.
Its technology uses natural language processing and algorithms that learn from threats it sees across its client base, and it uses that learning to simultaneously remove malicious content from other sites.
Twitter has automatic and manual controls to help identify malicious content on the site, and last year Twitter sued those responsible for five of the most-used spamming tools on the site.
