Nothing is secure TBH - it's like code-breaking or the radar wars during WW2
The Bad guys break the code, the good guys improve things - but it never lasts .
The world (outside NK) is totally connected, too many brains at work, too many ways in, too many lazy people (remember a big ENIGMA break was the realisation that operators often signed off with "HH" - Heil Hitler..), too much incentive if you are inside to join the Dark Side.....................................
All you can do is stay alert and use the maximum amount of security you can