Which of the following actions should be taken first after a security breach?

The first action that should be taken after a security breach is to contain the breach. Containment is critical because it involves taking immediate steps to stop the ongoing unauthorized access or damage. This might include isolating affected systems, shutting down compromised accounts, or blocking network access to prevent the breach from spreading further.

By addressing the breach immediately, organizations can mitigate the potential damage and protect sensitive information from being further exposed. Once containment is achieved, organizations can then assess the damage, notify affected parties, and implement measures to prevent future breaches. Prioritizing containment ensures that the incident is managed effectively and the organization can begin to recover from the breach without allowing further data loss or system impairment.