According to the NH Union Leader, the fact was discovered on August 24, when the cable connecting the two networks was spotted by one of the prison's staff.
The investigation into the breach, lead by the Department of Corrections (DOC) Investigations Team and the state's Department of Information Technology, is still under way, so many details are unknown.
“Corrections staff discovered a security breach of a cable, which connects an internal computer network to work stations, located in the Correctional Industries area of the prison. The area was secured and the shops were closed," explained New Hampshire Department of Corrections spokesman Jeff Lyons.
2This network is mainly used to track invoices and billing for Correctional Industries contracts. The server on which this data is maintained is a stand alone server from the DOC network, which also supports the offender management database system otherwise known as the Corrections Offender Records and Information System (CORIS). However, the breach resulted in the two networks being connected. The criminal investigation will determine the cause of the security breach and whether any data was compromised.”
He also pointed out that CORIS is password protected, as well as most other data on the DOC network, so this could have considerably hindered the inmates' capability to modify anything. On the other hand, if they somehow managed to get their hands on those passwords, they could have easily accessed and changed parole dates, sentencing information, programming schedules for inmates, staff information, and more.
The investigation will hopefully offer some insight into how long the two networks were connected, how the inmates managed to connect them without the staff noticing anything, and what information - if any - they were able to access.