Clinton Watts, a former F.B.I. agent who has tracked suspected Russian activity on Twitter for several years, said the platform had proved especially vulnerable to abuse, in part because the company demands little information from users. Twitter was used for years by the Islamic State for propaganda and recruiting, though much of that activity has now been shut down.
“Bad people can do what they want on this platform,” said Mr. Watts, a senior fellow at the Foreign Policy Research Institute in Philadelphia. “I think they have real problems trying to trace the Russian activity.”