Friday's Winter Olympics opening ceremony in Pyeongchang came under cyber attack from malware known as "Olympic Destroyer." The virus affected Internet and television services used by media representatives but did not cause any major long-term disruption.
https://www.notebookcheck.net/Olympic-Destroyer-virus-fails-to-destroy-Olympics.282706.0.html
Or it could have been US-directed actors, very angry over South Korea engaging with the North without USA's direction and actually against US political interests.
The US government of Trump (but in accord with former Obama officials), even went as far as to sabotage the symbolic gestures (common Olympic team, meeting between high-ranking officials) by
- stationing more nuclear weapons in Guam
- putting the Hawaii base at (false) high alert
- staging an "anti-north" event
- sending Pence over to cast a diplomatic shadow all over the North-South meetings
The US views the new South Korean leader (who was elected on a peace-platform, after the former US puppy was quickly dismissed over corruption, which did not really bother the Us govt) as "Weak", exactly because he does not promote US geo-strategy.
This is what US official have to say:
""If South Koreans are viewed as running off the leash, it will exacerbate tension within the alliance""