One of the functions of the Network Operations Group had was managing the IBM Mainframe network.  Let’s say 2,500 terminals in all.

Now, back in those days, there was a 2% training levy that employers were required to spend on their employees.  So our management thought

We could send the Network Operations team to learn NetMaster.

NetMaster, later known as Solve:NetMaster, is a product which allows you to manage IBM Mainframe Networks.  Sure YOU CAN manage the network from a System Console (SysCon), but NetMaster makes it easier to do.

The other thing NetMaster could let you do is string commands into a batch file, so you could do complex network tasks.  Very useful in the right hands.

Enter the Newly Trained Operator, keen to see what all these scripts in front of him could do.  So, one by one, he ran them.  Everything went well until he reached Z.

Specifically the ZNET script.

Newly Trained Operator entered
and pressed ENTER.

The console screens filled with errors, the 30 transaction log printers all started up at the same time, and the phones started ring.

Some clever Systems Programmer created ZNET to do a “Z NET, CANCEL”.  The reasons for doing so are lost in time.
Z NET, CANCEL forces the network to shutdown RIGHT NOW.  Kind of like unplugging your computer from the wall socket, without turning it off first.

The cost?  Whole branch banking and ATM network fell over, costing over $1 million and 2 hours downtime.

The following day?  Security permissions were applied to the NetMaster scripts.