It works by looking for traffic flows where one system forwards requests or sessions between two other endpoints instead of interacting directly. Defenders use it to spot proxying, lateral movement, credential relay and command channels hidden behind intermediaries. Useful signals include repeated hops, unusual source-destination pairs and consistent forwarding behaviour over time.
How relay pattern analysis detects forwarding paths
relay pattern analysis looks for an intermediary that is not the real endpoint but is repeatedly carrying traffic between two others. The analyst is trying to distinguish normal routing or proxy infrastructure from suspicious forwarding behaviour, especially when the flow pattern suggests hidden access, credential relay, or a command channel. A MITRE D3FEND Guide is useful here because the same technique family covers relay, proxying, and related defensive countermeasures.
The analysis usually starts with flow metadata rather than payload inspection. Repeated hops, stable source-destination pairings through a middle system, and forwarding behaviour that stays consistent over time are all signals that the middle node is acting as a relay. That matters because a relay can hide the true initiator, mask lateral movement, or carry session traffic in a way that defeats simple origin-based detection.
Good analysis separates benign intermediaries from suspicious ones by asking whether the forwarding role is expected. Proxies, load balancers, bastions, gateways, and message brokers can all forward traffic legitimately, so the question is not merely whether relaying exists, but whether the pattern, timing, and peers match the system’s intended function. The stronger the mismatch between declared role and observed traffic path, the more useful the pattern becomes for detection.
What defenders look for in relay traffic
Useful indicators often come from graphing connections over time and looking for repeated path shapes. A relay stands out when one host appears as a transit point for endpoints that should normally communicate directly, or when the same middle system keeps appearing in flows that involve authentication, administration, or sensitive back-end access. A second useful lens is protocol consistency: traffic that is forwarded cleanly without the middle host behaving like a true application endpoint is often more suspicious than ordinary application traffic.
Relay analysis is especially valuable when it is combined with account and host context. If a relay is carrying sessions that line up with unusual logons, stale credentials, or access from an unexpected host, the pattern can point to credential relay or post-compromise pivoting. MITRE ATT&CK Enterprise Matrix is a strong companion reference because relay behaviour often sits alongside credential access, lateral movement, and defence evasion techniques.
Defenders also look for a stable forwarding role that appears only under certain conditions, such as during privileged access, remote administration, or automation runs. That can indicate a hidden command channel or a control path that is only activated when an operator or adversary needs it. When the relay exists only for some sessions, not all, the inconsistency itself becomes a detection clue.
Why relay patterns matter for incident detection
Relay patterns matter because they can reveal abuse of trust, not just network structure. A system that forwards traffic may be acting as a proxy, but it may also be masking the true source of actions, extending access beyond intended boundaries, or relaying authenticated sessions into systems that should never be directly reachable. For that reason, relay analysis is often paired with segmentation checks and access-path review.
When the issue involves an API or service path, authorization and routing assumptions are especially important. A relay can turn a direct access model into an indirect one, which changes who appears to be calling what and can confuse monitoring that only trusts the observed source IP. NIST Cybersecurity Framework 2.0 is relevant at the governance level because relay detection supports monitoring, logging, and response objectives even when the underlying traffic is otherwise ordinary.
In practice, relay analysis is strongest when it is treated as a pattern-recognition problem, not a single alert type. One suspicious relay is often less important than a cluster of flows that share the same intermediary, the same timing, and the same destination set. That clustering is what helps distinguish an attacker-built relay path from a legitimate hop in a normal enterprise architecture.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
MITRE ATT&CK addresses the attack and risk surface, while NIST CSF 2.0 sets the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| MITRE ATT&CK | T1090 — Proxy | Relay analysis centers on intermediary forwarding and hidden access paths. |
| T1021 — Remote Services | Relay traffic often supports lateral movement and remote administration paths. | |
| Recommendation — Map relay-like flows to T1090 and inspect the intermediary for pivoting or concealment. Correlate relay paths with remote service use to spot lateral movement. | ||
| NIST CSF 2.0 | DE.CM-01 — Monitoring for Unauthorized Personnel, Connections, Devices, and Software | Relay detection depends on identifying unexpected connection paths and intermediaries. |
| Recommendation — Tune monitoring to flag unexpected intermediaries and abnormal connection paths. | ||
Practitioner Guidance
What to verify: Confirm whether the intermediary is supposed to forward traffic for the observed protocol and destination set. If the host is not a documented proxy, gateway, broker, or jump path, treat the forwarding pattern as an investigative lead rather than normal routing.
What to measure: Track repeated source-destination pairs, hop reuse, and session timing around privileged or sensitive flows. A rise in stable forwarding relationships through the same middle host is often more actionable than one-off anomalies.
Common mistake: Do not stop at “it is a proxy.” Legitimate intermediaries and malicious relays can look similar at the packet level, so the key judgement is whether the behaviour fits the system’s approved role and access model.
Practitioner takeaway: Relay pattern analysis is most useful when you combine network topology, role expectations, and session context, because the suspicious signal is usually not the hop itself but the mismatch between the hop and the system’s expected function.