By Zoey Chong writing for CNET
From the article,
They could be among the nearly 48 million bots on Twitter, according to a study by the University of Southern California and Indiana University. The study, which used more than 1,000 features to identify bot accounts on the site across six categories, estimated that between 9 percent and 15 percent of Twitter's active monthly users are bots. Using Twitter's most recent figure of 319 million active monthly users, that translates into 28.7 million to 47.9 million bots. The higher-end figure is significantly higher than Twitter's own bot estimate. A Twitter spokesman declined to comment Tuesday other than to point to a Securities and Exchange Commission filing on Feb. 27. In the filing, Twitter restated its previous estimate that 8.5 percent of its active monthly users are automated accounts. According to Twitter's figure, just over 27 million of its accounts are bots.