CHAIN-113 — Subnet without NSG and with a publicly-reachable VM

Summary

Severity: Critical · Likelihood: Medium · Logic: ALL

Why this chain matters

A subnet has no NSG attached and contains a VM with a public IP. Azure network security boils down to 'the VM's OS firewall', which is often Windows Firewall exclusions or permissive Linux iptables. Any service the VM runs is internet-reachable.

Component rules

This chain fires when its trigger conditions are met by the following rules. Click any rule to see its detection logic and compliance mappings.

Rule ID	Role
zt_net_011	Trigger
zt_net_001	Trigger

Attack walkthrough

Step 1 — Port-scan the VM's public IP; find an exposed service.

Actor: Attacker
MITRE ATT&CK: T1595.001
Enabled by: zt_net_011

Attacker gain: Service discovery.

Step 2 — Exploit the service or brute-force its auth.

Actor: Attacker
MITRE ATT&CK: T1190
Enabled by: zt_net_001

Attacker gain: VM compromise.

Blast radius

Initial access	Internet scan.
Max privilege	Full VM RCE.
Data at risk	VM filesystem, MI token
Services at risk	The VM + anything its MI can reach

How the logic works

The chain fires only when every rule above has at least one finding in the current scan. Missing any one rule breaks the chain — so remediating any single step disrupts the attack path.