Final answer:
Sarah was engaging in network monitoring to ensure network security, but none of the provided options (STIX, IOC, Telnet, HTTP) directly describe the act of noticing substantial outbound network traffic.
Step-by-step explanation:
When Sarah, a network security administrator, noticed substantial outbound network traffic while going through the network log, she was performing network monitoring, which is a process generally aimed at ensuring the integrity, confidentiality, and availability of network services.
Among the given options, the correct term associated with Sarah's activity is not specified. STIX (Structured Threat Information eXpression) and IOC (Indicators of Compromise) are related to threat intelligence. Telnet is a network protocol used to provide bidirectional interactive text-oriented communication facility, and HTTP is the protocol used for transferring web pages on the internet.
Therefore, Sarah's activity of noticing substantial outbound network traffic can indicate that she may be concerned with a security analysis task, which might include identifying IOCs or anomalies in the traffic but is not represented by any of the options provided.
The activity that Sarah performed while going through the network log is Telnet.
Telnet is a protocol that allows you to remotely access and manage devices on a network. By observing substantial outbound network traffic, Sarah was able to identify that Telnet was being used to establish connections to remote devices.