Network isolation techniques are immediately implemented after a security breach to:

 Network isolation techniques are immediately implemented after a security breach to reduce the extent of further damage by limiting the access and communication of the compromised systems or networks with the rest of the environment. This can help prevent the spread of malware, the exfiltration of data, or the escalation of privileges by the attackers. Network isolation techniques can include disconnecting the affected systems or networks from the internet, blocking or filtering certain ports or protocols, or creating separate VLANs or subnets for the isolated systems or networks. Network isolation techniques are part of the incident response process and should be performed as soon as possible after detecting a security breach. References = CISM Review Manual 15th Edition, page 308-3091; CISM Review Questions, Answers & Explanations Database - 12 Month Subscription, Question ID: 1162