Washington (CNN)-- A computer hacker responsible for creating and operating a massive scam that infected as many as 12 million computers worldwide has been identified and arrested, authorities said Wednesday.

The FBI said in a news statement a 23-year-old Slovene known as "Iserdo" was arrested last week for his role in a cyber scam that stole passwords from websites and financial institutions. Authorities believe the Slovenian citizen is responsible for creating and selling the Mariposa botnet.

Botnets are a network of computers infected with a malicious kind of robot software which allow remote access, often without the owner's knowledge.

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