Elasticsearch can be effectively utilized for network security monitoring, specifically for detecting TCP host portscans, by leveraging its speed, scalability, and flexibility. The process involves capturing network traffic data using tools like tcpdump, structuring event data with Logstash, and indexing it in Elasticsearch. Aggregations within Elasticsearch help detect suspicious activity, such as a high number of unique port connections in a short timeframe, indicative of a portscan. To automate alerts, the Watcher feature can be configured to send email notifications when predefined conditions are met, such as detecting more than 50 unique port connections from a source to a target within 30 seconds. This approach demonstrates how Elasticsearch's capabilities can be adapted for robust security monitoring and proactive threat detection in large organizations.