This read-write enumeration sets the monitor (source) port's mirroring mode to txOnly, rxOnly, rxAndTx, or disabled, determining what traffic on that port gets copied to the destination sniffer port, and it can't be changed while portMirrorStatus is disabled. Admins use it to control exactly which direction of traffic on a suspect port gets captured. For instance, setting portMirrorSourcePort to rxAndTx on a compromised host's port lets an admin capture both inbound and outbound traffic for forensic analysis.