Defending Your Network Edge in New Zealand (and beyond)
Zero day threats targeting network edge infrastructure are evolving faster than many organisations can respond. Firewalls, VPN concentrators, load balancers, SD-WAN appliances, and virtual desktop infrastructure gateways are frequently positioned as the first line of defence. These systems were once treated as “set and forget” assets. In practice, they are often excluded from routine patching, overlooked during architecture reviews, and sit outside the scope of most detection tooling. This makes them an ideal entry point for adversaries with the right exploit.
This article reflects lessons drawn from hands-on posture assessments, architecture reviews, and incident response engagements across enterprise, government, and infrastructure-heavy environments. While the original version was published during my time at Sygnia, this expanded edition is written with Aotearoa New Zealand in mind. The tools and timelines may differ, but the risk profile is consistent. Teams here face the same challenge: protecting systems that appear stable but are quietly exposed.
TL;DR
Network edge infrastructure is increasingly targeted by both opportunistic and advanced attackers. Firewalls, VPN concentrators, load balancers, and VDI gateways are often overlooked as Tier-Zero assets, even though they control access and enforce policy for the rest of the environment.
This guide offers both immediate and strategic actions to improve edge security, drawn from real-world consulting, assessments, and incident response work. It covers:
Reducing internet-facing exposure and patching vulnerabilities quickly
Locking down management interfaces and enforcing least privilege
Monitoring for system file changes and misconfigurations
Enhancing log forwarding, detection, and failover readiness
Transitioning from VPN to Zero Trust models
Segmentation, SaaS adoption, and proactive posture reviews
Zero Day Fire Drills at the Network Edge
These cases illustrate real world zero day incidents that triggered global response and pressured organisations into emergency remediation. They are not theoretical exercises. They are operational crises that exposed deep gaps in edge visibility, incident response readiness, and architectural assumptions. In nearly every case, attackers bypassed standard detection controls by targeting infrastructure that was assumed to be stable, secure, or out of scope for continuous monitoring. Once inside, they leveraged the inherent trust placed in these systems: VPNs, firewalls, load balancers, and remote access gateways. This allowed them to escalate access, pivot laterally, or remain persistently undetected.
For organisations operating in New Zealand, these examples serve as a cautionary mirror. While some threat actors may appear focused on global targets, the same techniques apply locally, especially in under resourced environments with ageing infrastructure or limited visibility into appliance level activity. If your firewall or remote access gateway cannot generate reliable logs, support modern authentication, or alert on misuse, it may already be compromised. And no one would know.
CitrixBleed | CVE 2023 4966
A memory disclosure flaw in Citrix NetScaler ADC and Gateway allowed unauthenticated attackers to harvest credentials and hijack sessions in live environments. Adversaries used this access to bypass authentication and impersonate users. The exploitation persisted well into 2025 and affected sectors including healthcare and government. Vendor Advisory | Research Analysis
Operation MidnightEclipse | CVE 2024 3400
A command injection vulnerability in PAN OS GlobalProtect Gateway, exploitable when telemetry was enabled. Threat actors executed arbitrary commands remotely without authentication. The Volexity team identified it in a targeted intrusion campaign known as Operation MidnightEclipse. Attackers manipulated routing and gained internal access via compromised firewalls. Vendor Advisory | Research Analysis
Ivanti VPN Exploitation Chain | CVE 2025 22457
A stack based buffer overflow in Ivanti Connect Secure and related appliances. This vulnerability enabled unauthenticated remote code execution and was used to install persistent malware implants. Exploitation bypassed identity enforcement and allowed deep network access through a trusted remote access path. Vendor Advisory | Research Analysis
Check Point VPN Portal Exposure | CVE 2024 24919
An unauthenticated information disclosure vulnerability in Check Point Security Gateway remote access portals. Attackers were able to extract sensitive credential materials and access tokens. This allowed domain escalation and lateral movement within corporate networks. Vendor Advisory | Research Analysis
Velvet Ant Campaign | CVE 2024 20399
A China aligned threat group exploited Cisco ASA, FTD, and Nexus switches using a command injection vulnerability. Attackers gained root level access and installed persistent malware without triggering alerts. Edge devices provided a stealth foothold with minimal telemetry, and in some cases remained compromised for over a year. Vendor Advisory | Research Analysis
WannaCry | MS17 010 (EternalBlue)
WannaCry was a globally destructive ransomware worm that exploited a vulnerability in Microsoft’s SMBv1 protocol (EternalBlue), originally disclosed in leaked NSA tools. It spread autonomously across networks using unpatched Windows systems. Although a patch was released weeks prior, many organisations failed to apply it to legacy servers or infrastructure appliances running embedded Windows. From an adversary’s standpoint, it provided mass propagation with no authentication or user interaction. Organisations faced encrypted data, halted operations, and widespread business disruption. Vendor Advisory | Research Analysis
The Campaigns Will Continue
These examples are not historical footnotes. They represent an ongoing pattern. Edge infrastructure continues to attract adversaries because it offers a unique combination of visibility gaps, operational importance, and persistent misconfigurations. Even well resourced teams struggle to monitor, patch, and control these systems in real time, especially when they sit outside the traditional endpoint or cloud perimeter.
The threat is not going away. As more organisations modernise, adopt hybrid work, and rely on VPNs, VDI gateways, and remote access firewalls, the attack surface at the edge continues to expand. Every new zero day becomes a live fire readiness test. Every missed patch becomes a potential pivot point for an adversary. Treating the edge as part of your core security estate, not a legacy blind spot, is no longer optional.
Misconfigurations in the Wild
Not every compromise at the edge requires a zero day. In many of the environments I have assessed across enterprise, government, and infrastructure-heavy networks, misconfigurations were just as dangerous. These are not theoretical risks. They are recurring patterns observed during real-world posture assessments, architecture reviews, and incident response work. In many cases, attackers did not need advanced tooling. The door was already open.
Exposed Management Planes
Management interfaces are often accessible from the internet due to oversight, legacy configurations, or unclear ownership. These interfaces may have been used during deployment and then forgotten. In multiple cases, we found them reachable with default or weak credentials and no multifactor authentication. Once accessed, they offered privileged control over network routing, logging configurations, and user authentication. These interfaces were rarely monitored and typically sat outside the endpoint or SIEM coverage.
In well-structured environments, firewall rules can prevent direct access to the management plane if it runs on a non-standard port. If not, the appliance should still support IP allowlists or hardened profiles to limit exposure. Ideally, teams should route access through secure jump servers or proxies, controlled by privileged access management systems like CyberArk. Microsegmentation tools can also restrict management traffic to known operator paths and reduce lateral movement options.
Legacy Services and Unused Entry Points
Firewalls and SD-WAN appliances frequently retain services that were deployed temporarily but never removed. In one case, I found a GlobalProtect VPN portal live on a Palo Alto firewall that the client had migrated away from months earlier. No one decommissioned it, no alerts were triggered, and no monitoring tools flagged the exposure. These dormant entry points become convenient footholds for attackers scanning for low-effort wins.
At another site, load balancers were left accepting external traffic for test applications that no longer existed. No authentication was required to reach the listener. It routed to nothing useful internally, but it still reflected infrastructure intent and confirmed service availability to external recon tools.
Citrix and Virtual Desktop Gaps
Virtual desktop infrastructure is often seen as a secure perimeter break, especially in regulated sectors. But the assumption rarely matches reality. I have seen environments where copy and paste between virtual and local machines remained enabled long after initial deployment. Combined with weak application controls, this allowed adversaries to introduce tools, payloads, and encoded scripts into otherwise restricted sessions.
In one case, a user downloaded a PDF in a Citrix session and opened it with the system viewer. This triggered a file explorer launch, allowing access to mapped drives and registry keys. There were no policies blocking these workflows. Startup scripts and scheduled tasks were editable by standard users, creating an easy privilege escalation path during post-exploitation.
Default Credentials and Forgotten Access Paths
Many appliances still ship with default administrator credentials. These are meant to be changed on first login, but often are not. In several client environments, we identified edge systems that still used the integrator’s original admin account. In one case, it was tied to a service ticketing platform that no longer existed. No one could say who owned the account, but it still worked.
When internal networks lack segmentation, a compromised edge device can become a launchpad. Attackers authenticate once, pivot to internal identity systems, and begin lateral movement without needing to reauthenticate. Edge-to-core transitions are rarely logged with sufficient granularity to detect this pattern unless the organisation has invested in real-time identity-aware inspection.
Configuration Drift in Complex Environments
Even mature teams face drift. Under pressure to restore uptime or respond to shifting business needs, changes are made without proper review. In one environment, SD-WAN rules were updated during a partner onboarding project, but no rollback plan was created. The result was an overly permissive route that allowed external access into the edge device’s local CLI shell.
Firewall changes during outages, load balancing policies adjusted during expansion, logging suppressed to address performance issues. All of these create drift. That drift often results in blind spots that persist until someone tries to exploit them, or until we show up to test them.
Treat the Edge as a Tier-Zero Asset
The network edge is no longer just a boundary. It is a control plane. Firewalls, VPN concentrators, SD-WAN appliances, and load balancers are used to enforce access, authenticate users, broker trust, and inspect traffic. That makes them operationally critical, not just in terms of availability, but in terms of integrity. If one of these devices is compromised, the blast radius includes everything behind it.
From a modern Zero Trust perspective, these devices are risk multipliers. They sit in the transaction path between users and systems. They make trust decisions on behalf of your core environment. If an attacker controls the edge, they can impersonate internal users, manipulate routing logic, and bypass access controls entirely.
This is why the edge must be treated as Tier-Zero infrastructure. The same way you protect identity providers, domain controllers, certificate services, and secure enclave platforms, you must protect the edge. That means putting it under full change control. That means segmenting access, logging every administrative action, and inspecting every authentication event for anomalies. Most of all, it means acknowledging that these devices can no longer be treated as passive infrastructure.
In consulting engagements, we often helped clients understand that Zero-Trust is not just a control strategy. It can also be a risk transfer model. The more responsibility you push onto edge devices, the more they become security chokepoints. This creates a need for defensive depth, operational discipline, and visibility parity. You cannot shift risk to the edge without also investing in its defence.
Immediate Defence Tactics
These measures can be implemented quickly to reduce exposure and increase resilience against edge device threats. They provide tactical coverage while your organisation moves towards broader strategies such as Zero Trust Network Access (ZTNA) and Secure Access Service Edge (SASE) models.
Minimise External Attack Surface
Identify and reduce internet-facing services. Prioritise patching and asset visibility for edge devices such as VPNs, firewalls, and load balancers. Use an External Attack Surface Management (EASM) tool to discover exposed systems, track risk, and guide mitigation.
Automating firmware and software updates using vendor tools such as Cisco’s Auto-Upgrade Manager can reduce manual effort and help maintain a secure perimeter. While this will not prevent every zero-day exploit, it does reduce the risk from known vulnerabilities being opportunistically exploited.
Secure the Management Plane
Many edge device vulnerabilities are linked to exposed management interfaces. These interfaces are often left online, unmonitored, or protected only by weak credentials and no multifactor authentication.
Restrict access to these interfaces internally, or if remote access is necessary, enforce strict IP allowlists and route all access through a hardened jump server. Ideally, manage this through a privileged access management (PAM) solution such as CyberArk. Segment management traffic from production flows and monitor it separately to detect abuse.
Limit Outbound (Egress) Traffic
If an attacker gains access to an edge device, they may attempt to maintain persistence using outbound command and control (C2) traffic. Tighten firewall rules to restrict outbound connections from the appliance itself. Do not rely on defaults. Enforce least-privilege access to external destinations and monitor for unexpected patterns or long-lived connections.
Monitor File Integrity on Appliances
Many compromises begin with quiet changes to startup scripts, web directories, or local logs. Enable file integrity monitoring on all edge platforms. Some vendors offer built-in tools, such as: Ivanti External Integrity Checker Tool or Fortinet Real-Time File Integrity Monitoring.
Where vendor support is limited, use third-party File Integrity Monitoring (FIM) tools like Tripwire, Varonis, or Netwrix, or export config baselines regularly and validate them offline. In one field case, a VPN gateway was backdoored using a modified boot script that disabled log forwarding. It remained undetected for weeks due to the absence of integrity checks.
Enforce Least Privilege Access
Limit administrative access to edge devices. Apply role-based access control (RBAC) where available. Avoid shared admin accounts and rotate credentials regularly. Conduct audits of access rights, especially during staff transitions or vendor engagements. These controls limit the blast radius if credentials are stolen or misused.
Improve Detection and Logging
Forward all system logs to your SIEM or threat detection platform. Ensure firewall, VPN, and SSL termination logs are retained and enriched with caller IP headers such as X-Forwarded-For. Retain logs long enough to support retroactive investigations.
Where supported, enable built-in intrusion prevention or detection features on appliances. Supplement these with external IDPS sensors to detect suspicious traffic patterns or exploitation attempts.
Design for Availability and Patchability
Build your edge infrastructure with redundancy in mind. Configure high availability (HA) pairs, establish failover routines, and rehearse the process. The ability to quickly patch or replace an edge device without downtime makes rapid remediation possible, especially when zero-day threats emerge.
Strategic Defence Approaches
These longer-term measures address underlying architecture and security culture. They reduce systemic risk and improve your ability to contain, detect, and respond.
Shift from VPN to ZTNA
Legacy VPNs expose too much surface area. Transition to Zero Trust Network Access (ZTNA) solutions that verify user identity, device health, and risk context before granting access. Cloud-based ZTNA providers allow fine-grained control, obfuscation of internal services, and detailed access logging.
Begin with a phased rollout by mapping internal services and segmenting access for a limited user group. Gradually replace legacy VPN flows with policy-based ZTNA access.
Segment Internal Networks
Flat networks enable lateral movement once an edge device is compromised. Introduce segmentation between business units, user types, and application tiers. Apply this approach to cloud networks as well. Deploy microsegmentation or firewalls that restrict movement using protocols like SSH, SMB, RDP, or WinRM. Monitor cross-zone traffic and investigate anomalies promptly.
Prefer SaaS Over Self-Hosting
Self-hosted business apps are often unpatched and misconfigured. When possible, migrate email, document collaboration, and workflow platforms to SaaS offerings. This reduces the management burden and shifts patching responsibility to the vendor.
This approach is not risk-free, but it does limit exposure to local vulnerabilities and helps enforce identity-based access.
Conduct Routine Security Assessments
Posture assessments, design reviews, penetration tests, red teams, and threat hunts all provide valuable visibility. These help uncover overlooked risks, prioritise remediations, and build consensus among technical and leadership teams. Schedule regular assessments and integrate their findings into your broader risk programme. Even partial implementation of recommendations can drastically reduce exposure.
Final Thoughts
Edge threats are not going away. The growing complexity of infrastructure, adversary tooling, and exploit automation means your edge systems are a constant target. The recent wave of zero-days against Citrix, Ivanti, and Fortinet appliances is only the beginning. By combining short-term hardening with strategic transformation, you can make it much harder for attackers to succeed and easier for your team to detect and respond when they do.
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