Something doesn’t make sense… I have a number of questions. I work in IT and there’s additional important details to understand… is this planned or unplanned outage and what type of switchover is involved. I can only assume it’s unplanned and involves servers and probably a database(s) and needing to export and potentially transform / load data to the new system. Has a critical server failed and they are waiting for delivery of a new box?
If it’s planned why the need to shut down for 3 weeks? They should run production for longer or have a backup to use while working on the update/ upgrade. If it’s unplanned what is the timeframe based on? And is there not a clean backup they can use in the meantime?
Also, at what level is this occurring? I’d think it would be at a national level as opposed to international… each level should be secure but hackers are resourceful and employees are fallible. Note, I have no idea if they were hacked or not I’m speculating on the 3 week outage.