“According to the email our cyber experts sent to our teams, they believe a hacker tool Metasploit was used,” it continued.

Metasploit, an open-source project used to find vulnerabilities in software, is reportedly very easy and cheap to develop.

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“There was also some music playing randomly on several of the workstations during the middle of the night with the volume maxed out,” the e-mail reads. “I believe it was playing ‘Thunderstruck’ by AC/DC.”