SAN JOSE, Calif. (AP) – Twitter’s been having a rough couple of weeks.

A researcher looking into the attacks that knocked Twitter offline last week discovered another, unrelated security problem.

At least one criminal was using a Twitter account to control a network of a couple hundred infected personal computers, mostly in Brazil. Networks of infected PCs are referred to as “botnets” and are responsible for so much of the mayhem online, from identity theft to spamming to the types of attacks that crippled Twitter.

The discovery was made by Jose Nazario with Arbor Networks. The affected Twitter account was taken down. Twitter didn’t immediately respond to e-mails from The Associated Press.