What are common mistakes with Virtual Private Network?

Where Virtual Private Network Configurations Usually Go Wrong

The most common mistakes are not about the tunnel itself, but about the trust decisions around it. A VPN becomes risky when teams treat connection as proof of safety, leave gateway authentication too weak, or fail to harden the appliance that terminates remote access. A connected user or device should still be assumed untrusted until policy, device posture, and logging say otherwise.

Another frequent failure is over-broad post-connection access. If the VPN drops a user onto a flat internal network, it can turn remote access into a shortcut for lateral movement. That is why the design of the network path matters as much as the encryption in transit. Network ports and protocols security is often the right lens for understanding what the VPN is really exposing behind the gateway.

Operational mistakes matter too. Devices that are not patched, split tunnelling choices that are not deliberate, and weak visibility into VPN sessions all create avoidable exposure. For a deeper, VPN-specific checklist, see the VPN Security Guide.

How Weak VPN Authentication and Segmentation Create Real Exposure

A VPN mistake becomes security-relevant when it converts remote access into implicit internal trust. Weak authentication at the gateway, stale credentials, or poor device verification can let an attacker use a valid connection path without proving the endpoint is safe. Once inside, excessive network reach can expose file shares, admin interfaces, internal apps, and legacy services that were never meant to be reachable from a remote connection.

Split tunnelling is another design choice that often changes the threat model. If a remote endpoint can talk to both the internet and the internal network at the same time, malware or an attacker who gains access on the device may be able to pivot between those paths. The issue is not split tunnelling in isolation, but whether the organisation can still enforce segmentation, inspection, and identity-based access decisions after the tunnel comes up.

Logging is part of the control surface, not an afterthought. Without session logs, device context, and authentication telemetry, it becomes hard to tell whether a login is routine remote work or an account being abused from an untrusted endpoint.

What Good VPN Hygiene Looks Like in Practice

Good practice starts with limiting what a VPN user can reach after authentication. The safest pattern is to grant only the specific network paths and applications needed for the task, not a broad internal route by default. That usually means treating the VPN as a transport layer, then layering authorization, device checks, and monitoring on top of it.

It also means maintaining the gateway like any other high-value edge service. Patch quickly, remove weak authentication options, review exposed management surfaces, and verify that backup access paths are not more permissive than the primary one. A generic remote-access design often fails because the organisation secures the login page but not the downstream network reach.

For teams comparing VPN-heavy remote access with tighter access models, the important question is whether the connection should expose a network or only an approved application path. That choice determines how much lateral movement is possible if a credential or endpoint is compromised, and it should be made deliberately rather than inherited from legacy architecture. The Top 10 Network Security Misconfigurations guide is useful when you want to review the adjacent exposure patterns that make VPNs harder to defend.

Risk and Threat Considerations

VPN mistakes matter because they can turn a single compromised credential, endpoint, or appliance into broad internal access. The common failure mode is over-trust: once the tunnel is established, defenders may stop treating traffic as suspicious and attackers may exploit that blind spot to move laterally or blend in with normal remote work.

Failure mechanism: Weak authentication, excessive network reach, and poor device validation let an attacker reuse a valid remote-access path to reach internal systems that should have stayed segmented.

Impact: A compromised VPN account or endpoint can lead to deeper internal access, weaker detection, and a much larger blast radius than the original remote-login event suggests.

Practitioner Guidance

What to verify: Confirm that VPN access is tied to strong authentication, device posture checks, and tightly scoped internal reach. If a connected user can see far more of the network than their role needs, the design is already too permissive.

What to measure: Track how many VPN sessions have access to more internal segments than necessary, how quickly appliances are patched, and whether session logs are detailed enough to support investigation. Those three signals usually show whether the control is real or only cosmetic.

Common mistake: Treating the VPN as the security boundary. In practice, the boundary is whatever the authenticated session can reach after connection, so network design and logging matter as much as the tunnel itself.

Practitioner takeaway: The safest VPN is not the one that connects most easily, but the one that still behaves like an untrusted path after login, with the smallest possible reach and the clearest possible evidence trail.

Related resources from NHI Mgmt Group

• What are the common mistakes teams make when rolling out private access tools across many environments?
• What are common mistakes with virtual machine hardening?
• What are common mistakes with virtual desktop infrastructure (VDI) security?
• How do you patch or mitigate CVE-2017-12319 (Cisco IOS XE Software Ethernet Virtual Private Network Border Gateway Protocol Denial-of-Service)?