Catastrophic events include those that are caused by both internal and external factors. A catastrophic event might be unanticipated, or it might be the result of a tracked high-risk event that could not be mitigated or contained.
Internal catastrophic events would include such things as the following:
Hardware or network failures
Large reductions in workforce
Losing one or more very large contracts or accounts
Loss of multiple team members at one time (perhaps a mass exodus to start a new company or join a competitor)
Privacy or security breaches that might become public knowledge
Faulty products that have to be recalled, or have caused harm, and for which there has been negative publicity
Environmental issues or damage ...