T1599.001Not expressible in Sigma

Network Address Translation Traversal

Defense ImpairmentNetwork Devices

Where this stands

No Sigma rule can address this — the telemetry MITRE names has no Sigma logsource behind it.

None of MITRE's analytics for this technique name a log source that maps to a Sigma logsource — they describe abstract data ("Process::None"), API-hook telemetry, or prose channels with no reliable field names behind them.

What the technique is

Adversaries may bridge network boundaries by modifying a network device’s Network Address Translation (NAT) configuration. Malicious modifications to NAT may enable an adversary to bypass restrictions on traffic routing that otherwise separate trusted and untrusted networks. Network devices such as routers and firewalls that connect multiple networks together may implement NAT during the process of passing packets between networks. When performing NAT, the network device will rewrite the source and/or destination addresses of the IP address header. Some network designs require NAT for the packets to cross the border device. A typical example of this is environments where internal networks make use of non-Internet routable addresses. When an adversary gains control of a network boundary device, they may modify NAT configurations to send traffic between two separated networks, or to obscure their activities. In network designs that require NAT to function, such modifications enable the adversary to overcome inherent routing limitations that would normally prevent them from accessing protected systems behind the border device. […]

Read it on attack.mitre.org

What MITRE says you would watch

AN0465
Defenders may observe unauthorized or anomalous changes to NAT configurations, including the addition of new translation rules or modifications to existing ones. Suspicious behaviors include sudden introduction of NAT mappings bridging segmented networks, new port address translation rules that obscure true source IPs, or traffic flows inconsistent with expected network design. Multi-event correlation includes detecting configuration changes on routers/firewalls, followed by traffic traversing unexpected internal/external address pairs.