A 23 year-old hacker responsible for a botnet that has infected millions of computers worldwide has been arrested in Slovenia. While his real name was not revealed, the man in question is known as ‘Iserdo’ and he is believed to have written the programme behind the mariposa virus, also known as ‘butterfly’.

The butterfly botnet (hey, you try and get a picture of a botnet) has infected nearly 13 million computers.

The botnet, one of the world’s largest, was dismantled earlier this year after infecting 12.7 million computers. It was designed to steal personal financial details and was also found in the PCs of banks and major companies.

Jeffrey Troy, deputy assistant director for the FBI cyber division told reporters that, “To use an analogy here, as opposed to arresting the guy who broke into your home, we’ve arrested the guy that gave him the crowbar, the map and the best houses in the neighbourhood.”

It wasn’t just the FBI that was after this bloke though. The BBC reports that “officials from around the world” have been working together to capture the criminals behind the massive malware operation. Indeed, in December 2009 three people believed to have been running it were arrested in Spain.

Security expert Rik Ferguson told the BBC that the mariposa botnet had got out of control. “They guys behind it said it was more successful than they had intended to be,” he said. “As is the case with most botnets, the more widespread they are the more likely they are to be discovered. They were a victim of their own success.”

Nobody has yet been arrested in connection with the Conficker worm, a similar virus which is currently running on six million Windows PCs and is believed to peaked at up to 12 million, Ferguson added.