Bypassing Network Segmentation

A subject bypasses logical or physical network segmentation controls (such as VLANs, ACLs, security groups, or subnets) in order to obtain unauthorized access to systems, services, or data across trust boundaries. This preparation technique commonly manifests through deliberate configuration changes (e.g., modifying ACLs or VLAN assignments), covert tunneling (e.g., SSH, HTTPS reverse tunnels), rogue device introduction (e.g., unmanaged switches or dual-homed devices), or misuse of trusted services (e.g., remote access platforms or admin automation tools that bridge zones).

Such actions are often observable via first-time or anomalous cross-segment flows, management plane configuration logs, 802.1X/NAC anomalies, or long-lived encrypted outbound sessions. These techniques typically exploit privileged access, weak change control, or poor posture enforcement.

This behaviour may be motivated by a subject’s attempt to escalate access, stage data for exfiltration, evade oversight, or maintain persistence across environments. It is especially critical in environments with sensitive zoning, such as production-to-dev separations, cloud VPC peerings, or physically segmented OT/ICS networks.

Investigators should prioritize telemetry correlation across NetFlow/IP Flow Information Export (IPFIX), EDR, DHCP, and identity systems to attribute cross-zone traffic to known assets and subjects. Preserve infrastructure configuration snapshots and identify whether segmentation was circumvented by direct administrative action, covert bridging, or software-level tunnelling.