Remote Procedure Call

How Remote Procedure Call Works

Remote Procedure Call, or RPC, is a communication pattern that makes a remote system look like a local function call. That abstraction is useful because it hides transport details, but it also means the caller often relies on network reachability, service discovery, and agreed interfaces rather than direct human interaction.

In practice, RPC is less a single product than a family of protocols and implementations. The security posture therefore depends on what sits behind the call, how the endpoint is exposed, and whether the caller is authenticated and authorised to invoke the requested action.

Why RPC Becomes a Security Boundary

RPC creates a boundary between a requesting process and a remote service, which is why it often becomes a control point for access, trust, and execution. When RPC is used to manage services or system actions, the call path can effectively become a remote execution surface if the target accepts it without strong trust checks or if exposed interfaces are reachable by an attacker.

That boundary matters because the danger is not only data access, but action. An RPC call may start a process, change a configuration, query a directory, or trigger an administrative function. In other words, the protocol is only the transport for the real risk, which is the authority behind the operation.

Common Failure Modes and Abuse Paths

RPC implementations are often vulnerable when they assume the caller is trusted, when authentication is weak, or when the exposed interface offers more capability than the caller should have. Attackers value RPC because it can provide a direct path to remote execution, privilege escalation, discovery of services, or lateral movement once a foothold exists.

Another recurring failure mode is exposure of management interfaces beyond the intended trust zone. When a service endpoint is reachable from hostile networks, defenders must assume the attacker can enumerate functions, test credentials, and look for logic that was designed for convenience rather than hostile input.

How Organisations Reduce Exposure

The first step is to know where RPC services exist, what they do, and who is allowed to call them. Asset inventory and interface mapping matter because RPC is often embedded in operating systems, middleware, and internal tooling rather than standing out as a single obvious application.

Exposure should then be constrained by network segmentation, strong authentication, and least-privilege service design. Where possible, RPC should be limited to the smallest possible trust zone, with administrative functions separated from ordinary application traffic and with tight control over which systems can reach the endpoint. For broader defensive mapping of RPC-style abuse patterns, MITRE ATT&CK Guide for Defenders helps defenders think in terms of adversary technique coverage, while Discovery and Reconnaissance Techniques Guide is useful when you are trying to detect how attackers enumerate exposed remote services before they attempt abuse.

Detection, Response, and Recovery Considerations

Because RPC is often used for legitimate administration, detection works best when defenders baseline normal callers, normal methods, and normal timing, then flag deviations. Unexpected administrative RPC activity, unusual source hosts, or a burst of remote method calls can indicate reconnaissance, abuse, or post-compromise movement.

If RPC abuse is suspected, review both the endpoint and the surrounding identity context. A remote call path that was abused may also imply stolen credentials, excessive permissions, or a trusted management account that needs review, because the protocol itself is rarely the only compromised component. External guidance such as NIST SP 800-53 Rev 5 Security and Privacy Controls and NIST Cybersecurity Framework 2.0 is useful here because both frame remote service exposure as a control, detection, and response issue rather than just a protocol detail.

Risk and Threat Considerations

RPC is risky when a remote interface is treated as a routine internal convenience but can actually execute sensitive actions. That gap between assumed trust and actual reachability is what makes RPC attractive to attackers and dangerous to defenders.

Failure mechanism: Exposed RPC services can accept remote requests with more authority than intended, especially when authentication, network filtering, or method-level authorisation is weak.

Impact: An attacker who reaches the interface may be able to run commands, change system state, enumerate services, or move laterally through trusted administrative pathways.

Practitioner Guidance

What to watch for: Treat RPC endpoints as privileged interfaces, not just plumbing. The main governance decision is who is allowed to call which methods from which systems, and that decision should be explicit rather than inherited from default network trust.

Practitioner takeaway: If an RPC service can change state, manage services, or trigger remote actions, review it with the same discipline you would apply to any other privileged control surface.

Related resources from NHI Mgmt Group

• How do you secure Microsoft Remote Procedure Call (MS-RPC)?
• Microsoft Remote Procedure Call (MS-RPC)
• Distributed Computing Environment / Remote Procedure Call (DCE/RPC)
• Windows Remote Procedure Call Runtime