How should IAM teams reduce lateral movement risk across users and service accounts?

Why lateral movement shrinks when access is tied to current function

Reducing lateral movement is mostly about removing unnecessary trust edges, not just tightening logins. If a user, service account, or integration can only reach the systems it currently needs, an initial compromise has fewer paths to pivot through. That means access reviews need to look at actual business function, cross-environment reach, and machine-to-machine dependencies together.

Least privilege is strongest when it is applied to the entitlement graph, not treated as a user-only policy. Application connections, shared automation, and dormant cross-domain grants often matter more than the primary account that was compromised.

How service accounts change the lateral movement problem

Service accounts often have broader reach than human users because they are created for uptime, not for bounded interaction. They may authenticate across environments, call back-end systems, or inherit old permissions that were never revisited after application changes. NHIMG’s Service Account Security Guide is a useful reference for treating those accounts as governed identities rather than technical leftovers.

The practical issue is that service accounts can become bridges between otherwise separate trust zones. Once an attacker lands on one compromised credential, a reused secret, broad token scope, or overprivileged integration can turn a single foothold into movement across systems. NHIMG’s Ultimate Guide to NHIs covers why overprivilege, unmanaged credentials, and visibility gaps are central to that risk.

The control question is not whether the service account is “needed”, but whether its access is still justified in its current form. If the account has cross-domain permissions, long-lived secrets, or indirect access to production data, it should be reviewed like any other high-impact identity. NHIMG’s NHI Lifecycle Management Guide maps well to that governance problem because lifecycle controls are where stale access usually accumulates.

What IAM teams should inspect in the entitlement graph

Start with the paths, not the labels. The same compromise behaves very differently depending on whether the account can only operate inside one application or can move across directories, cloud platforms, databases, and operational tooling. The most useful review is a path-based one: who can reach what, through which identities, with which secrets, and under what delegation model.

That is why access recertification has to include application-to-application relationships, not just named human users. If an integration depends on a service token, API key, or shared credential that outlives the business process it supports, it should be redesigned or constrained before the next incident forces the issue. NHIMG’s Ultimate Guide to NHIs — What are Non-Human Identities helps frame those machine-facing relationships as first-class identities.

Attackers also benefit from stale permissions that cross domains or roles. When a service account retains access to an old environment, or when a user still has rights from a prior function, the control failure is usually inheritance, not brute force. That is why the remediation priority is to remove stale cross-domain grants first, then trim overbroad current grants, then look at the authentication layer.

Risk and Threat Considerations

Lateral movement risk increases when organisations treat user access and service access as separate governance problems. Attackers often exploit whichever identity has the widest trust reach, and service accounts are attractive because they are rarely monitored as closely as humans but often connect to more systems.

Failure mechanism: Excessive entitlement, shared credentials, or unreviewed integrations create a path from one compromised account into adjacent systems, especially when the same secret or trust relationship is reused across environments.

Impact: The compromise can spread beyond the initial account, exposing data, admin consoles, automation pipelines, and production systems, while making containment harder because the attacker is moving through legitimate access paths.

Practitioner Guidance

What to prioritise: Review accounts that can traverse multiple systems, especially service accounts used by integrations, schedulers, and automation. Those identities usually produce the highest lateral-movement blast radius when they are overprivileged or long-lived.

What to verify: Confirm that each non-human credential has a current owner, a narrow purpose, an expiry or rotation plan, and no unnecessary cross-domain reach. If you cannot explain why the account needs a permission today, treat that permission as a candidate for removal.

Decision rule: If an identity can authenticate to more than one trust zone, enforce current-function access before you investigate whether it has already been abused. Reducing reachable paths is faster and more reliable than trying to detect every pivot in real time.

Practitioner takeaway: Lateral movement is reduced by shrinking the entitlement graph, not by focusing only on login hardening. The most effective teams govern service accounts and human accounts with the same discipline because attackers will use whichever path preserves the most trust.

Related resources from NHI Mgmt Group

• How should security teams manage generic service accounts in cloud environments to reduce lateral movement risk?
• How should organisations reduce lateral movement risk when users reuse passwords across personal and work accounts?
• How should security teams reduce lateral movement risk in Kubernetes clusters with shared controllers and service accounts?
• How should security teams reduce the risk of compromised VPN credentials leading to lateral movement across enterprise systems?