To prevent adversaries from intercepting response and recovery details. Using a secure method of communication during incident response is important to prevent adversaries from intercepting response and recovery details that could reveal the incident response team's actions, strategies, or findings. If the adversaries can intercept the communication, they could use it to evade detection, escalate their privileges, or launch further attacks. To ensure intellectual property remains on company servers, to have a backup plan in case email access is disabled, or to ensure the management team has access to all the details that are being exchanged are other possible reasons to use a secure method of communication, but they are not as important as preventing adversaries from intercepting response and recovery details. Reference: https://www.sans.org/reading-room/whitepapers/incident/incident-handlers-handbook-33901