O365 appears to be a huge improvement in Cyber Security over on-prem on a few points:
- Better vendor visibility of threat surface - Microsoft’s more than 300 person security staff has improved visibility to the threats posed to users of office products. They are able to see trending threats and react faster with fixes, patches and bulletins to customers.
- Higher patch compliance rates. Microsoft can patch O365 in the cloud all-at-once. In fact they re-build from "gold image" each time they implement a fix! This improves the overall security posture of the Office threat surface since the wait times are lower thus lowering zero-day exposure.
- Greater vendor support - Microsoft is able to provide significantly greater support in a managed service such as O365.
- O365 uses a no-trust model not offered in on-prem Office that improves security greatly.
- Encryption in the cloud further secures data.