Had this happen to a customer using one of the oracle cloud services.
https://www.theregister.co.uk/2018/01/09/oracle_weblogic_hole_primed_to_pump_monero/
Basically cronjobs were replaced with a crypto miner job and resources were maxed out.
The so called engineers at oracle cloud have NFI and did not communicate this to the customers.
Stay away from oracle cloud.