“Impersonation and deception are illegal under New York law,” Mr. Schneiderman wrote on Twitter. “We’re opening an investigation into Devumi and its apparent sale of bots using stolen identities.”

Image Eric T. Schneiderman, the attorney general of New York. Credit... Sasha Maslov for The New York Times

The investigation is the latest in a series of federal and state inquiries into the commercial and political abuse of fake accounts on social media. Tens of millions of fake accounts have been deployed to defraud businesses, influence political debates online and attract customers.

Social media companies, including Twitter and Facebook, have drawn intense scrutiny for not taking greater steps to weed them out. Many of the accounts identified by The Times appear to violate Twitter’s own policies, but remained active on the social media platform for years, each retweeting and promoting Devumi customers.

“The tactics used by Devumi on our platform and others as described by today’s NYT article violate our policies and are unacceptable to us,” Twitter said in a message posted on its media relations account on Saturday.

Mr. Schneiderman, who was first elected in 2010, has brought a series of cases focused on the emerging world of online fraud, impersonation and abuse. In December, he began an investigation into how the Federal Communications Commission was flooded with millions of fake comments on a proposal to scrap so-called net neutrality rules. Many of the comments used names and addresses borrowed from real people, almost always without their knowledge.