But perhaps the biggest point is that the three men were allegedly expert criminals, but not expert computer hackers. They bought the hacking tools they needed—such as the ability to send e-mails with a toxic payload to infect the computer of anyone who opens them—on the black market. Just as bank robbers do not need to make their own guns, cyber-criminals do not need to write their own malevolent software.

Source: What lies behind the JPMorgan Chase cyber-attack | The Economist