Edge Decay: How a Failing Perimeter Is Fueling Modern Intrusions

Modern intrusions increasingly target edge infrastructure, exploiting edge decay where perimeter devices like firewalls and VPNs become entry points rather than defenses. Attackers utilize zero-day vulnerabilities and automated tooling to compromise unmanaged edge devices, establishing persistent footholds bypassing traditional endpoint detection. The ArcaneDoor campaign demonstrates this risk by deploying the RayInitiator firmware bootkit on Cisco ASA devices, allowing survival through reboots and updates. Once inside, adversaries pivot to identity systems and virtualization platforms, harvesting credentials and intercepting authentication flows. This shift necessitates updated security strategies beyond perimeter hardening. Organizations must prioritize visibility into edge appliances, accelerate patch cycles, and monitor for firmware-level anomalies. Reliance on legacy boundary controls creates structural blind spots, enabling attackers to operate at machine speed and compromise enterprise identities from the network edge inward.

Edge devices are prime targets — learn how attackers exploit the perimeter to gain access, persist, and pivot to identity.

Modern intrusions increasingly target edge infrastructure, exploiting edge decay where perimeter devices like firewalls and VPNs become entry points rather than defenses. Attackers utilize zero-day vulnerabilities and automated tooling to compromise unmanaged edge devices, establishing persistent footholds bypassing traditional endpoint detection. The ArcaneDoor campaign demonstrates this risk by deploying the RayInitiator firmware bootkit on Cisco ASA devices, allowing survival through reboots and updates. Once inside, adversaries pivot to identity systems and virtualization platforms, harvesting credentials and intercepting authentication flows. This shift necessitates updated security strategies beyond perimeter hardening. Organizations must prioritize visibility into edge appliances, accelerate patch cycles, and monitor for firmware-level anomalies. Reliance on legacy boundary controls creates structural blind spots, enabling attackers to operate at machine speed and compromise enterprise identities from the network edge inward. Edge devices are prime targets — learn how attackers exploit the perimeter to gain access, persist, and pivot to identity. In the first blog of this series, we explored the Identity Paradox and how attackers exploit valid credentials to operate undetected inside enterprise environments. However, identity compromise rarely happens in isolation. To understand how these attacks begin, we need to look earlier in the intrusion lifecycle at the place many organizations still assume is secure: the edge. For years, cybersecurity strategy has been built around defending the perimeter to protect the enterprise. Firewalls, VPNs, and secure gateways were designed as the outer boundary of the organization – hardened systems intended to control access and reduce risk. But that model is breaking down. What was once treated as a defensive layer is now a frequent target of modern attacks. Rather than acting purely as protection, the perimeter increasingly introduces exposure. This shift reflects what can be described as edge decay, a gradual erosion of trust in boundary-based security as attackers focus on the infrastructure that defines it. The Perimeter Is No Longer a Safe Boundary The scale of this shift is hard to ignore. Zero-day vulnerabilities often target edge devices, including firewalls, VPN concentrators, and load balancers, all of which are not fringe systems. They are foundational components of enterprise connectivity, and the infrastructure that organizations built to protect themselves has become the infrastructure attackers exploit first. Yet, unlike endpoints or servers, many edge devices still sit outside traditional endpoint visibility and control. Because these appliances typically cannot run EDR agents, defenders are often forced to rely on logs and external monitoring instead. However, logging can be inconsistent, patch cycles are often slow, and in many environments, these devices are treated as stable infrastructure rather than active risk. This combination creates a persistent visibility gap. Attackers have recognized this gap and are exploiting it at scale. Rather than targeting hardened endpoints, adversaries are shifting their focus to unmanaged and legacy edge infrastructure and the systems that sit at the intersection of trust and exposure. Weaponization at Machine Speed One of the most significant accelerators of edge-focused attacks is the rise of automation and AI-assisted exploitation. Threat actors are no longer relying on manual discovery. Instead, they use automated tooling to scan global IP space, identify exposed devices, and operationalize vulnerabilities within hours of disclosure. In some cases, exploitation begins within days or even hours of a vulnerability becoming public. This compression of the attack timeline has important implications for defenders. Traditional patching cycles and risk prioritization models are no longer sufficient when adversaries can move faster than organizations can respond. As a result, edge compromise is increasingly observed as an early step in broader intrusion chains, often preceding identity-based attacks. Edge Devices as Persistent Beachheads Adversaries are increasingly prioritizing edge infrastructure because it represents a structural blind spot. Rather than targeting well-defended endpoints, they focus on unmanaged or legacy systems that fall outside standard visibility. Once compromised, these devices become more than just entry points, they provide a stable foothold for continued operations. Once attackers gain access to a firewall or VPN appliance, that system effectively becomes an internal pivot point rather than a boundary control. From there, adversaries can monitor traffic, capture credentials, and pivot deeper into the network. Investigations have repeatedly shown how compromised edge devices are used to: Intercept authentication flows and harvest credentials Deploy web shells on internal systems Create...