"The ability to create so many new accounts is classic Anonymous social-technological hacking,” Coleman said.
At the same time, millions of Twitter accounts began following longstanding Anonymous posters and retweeting them, helping boost Anonymous into Twitter's Trending column and greater attention.
But accounts using variations of the Anonymous name recently claimed credit for temporarily knocking a Minneapolis police website offline and, inaccurately, for hacking police passwords.
The amorphous internet activist movement known as Anonymous staged an online resurgence in the past week on the back of real-world protests against police brutality.
A Twitter spokeswoman said the company had seen no evidence of "substantial coordinated activity" among longstanding Anonymous accounts, but deleted one spammy new one brought to its attention by a researcher Tuesday.