Explanation
Cert Guide by Omar Santos, Chapter 9 - Introduction to digital Forensics. "When you collect evidence, you must protect its integrity. This involves making sure that nothing is added to the evidence and that nothing is deleted or destroyed (this is known as evidence preservation)."

After a breach has been discovered and the immediate threat has been addressed by identifying and removing the threat's access, the next step according to the NIST SP 800-61 Incident Handling Guide is to recover from the threat. This involves restoring systems to normal operation, confirming that the systems are functioning normally, and applying patches or other remediation measures to prevent similar breaches in the future1.
References :=
* Understanding NIST SP 800-61: The Computer Security Incident Handling Guide