Your firewall was supposed to be the wall between your organization and attackers. It is now the door they prefer to walk through. This is edge decay, the systematic exploitation of the infrastructure organizations built to protect themselves and it is happening to enterprises right now at scale.
What Is Edge Decay?
For decades, cybersecurity strategy was built around a simple premise: build a strong enough perimeter, and you’ll keep attackers out. Firewalls, VPN concentrators, load balancers, and secure gateways became that perimeter, the hardened outer boundary of the enterprise, designed to control access and reduce risk.
That model has not merely weakened. It has inverted. The devices organizations built to protect themselves have become the infrastructure attackers exploit first. Edge decay is the term for this gradual erosion, the point at which boundary-based security stops reducing risk and starts introducing it.
The perimeter isn’t failing, it’s already failed. Every unpatched VPN, every legacy firewall running decade-old firmware, every edge device outside your visibility is a door left open and forgotten.
SentinelOne Annual Threat Report, 2026
Unlike endpoints and servers, most edge devices cannot run modern endpoint detection and response (EDR) agents. They fall outside standard security monitoring. Patch cycles are slow, nobody wants to risk taking down the device the entire organization depends on for connectivity. The result is a growing population of trusted, under-monitored systems sitting at the exact intersection of your internal network and the open internet.
Edge devices are foundational to enterprise connectivity yet they typically sit outside endpoint visibility, run infrequent patches, and are treated as stable infrastructure rather than active security risk. Attackers recognized this gap years ago. Many organizations have not.
Why Attackers Are Targeting the Edge First
Adversaries are rational actors. They concentrate effort where defenses are weakest and the payoff is highest. Edge infrastructure checks both boxes precisely.
Machine-speed exploitation has outpaced human patch cycles
Modern threat actors no longer rely on manual discovery. Automated tooling continuously scans global IP space, identifies exposed devices, and operationalizes vulnerabilities within hours of public disclosure. Traditional patching timelines, measured in days or weeks — are no longer sufficient when adversaries can move faster than organizations can respond.
Edge devices sit directly inside authentication flows
Control a VPN appliance or firewall, and you gain something more valuable than mere network access: you gain a vantage point inside your target’s authentication infrastructure. Credentials, session tokens, and identity data flow through these devices. Attackers who compromise them don’t need to break authentication, they simply observe it.
Legacy infrastructure represents long-term, unresolvable risk
Many organizations continue to operate outdated edge appliances that lack modern security features, Secure Boot, robust integrity verification, or support for current security tooling. These “legacy ghosts” are stable, trusted by the network, and largely invisible to defenders. They are ideal targets: reliable footholds that the organization itself has effectively placed outside its own monitoring perimeter.
The scale of the shift is hard to ignore. Zero-day vulnerability disclosures increasingly target edge devices, not fringe systems, but the foundational components of enterprise connectivity that every organization depends on daily.
What Happens After Edge Compromise
When attackers compromise a firewall or VPN appliance, the device stops functioning as a boundary control and becomes an internal pivot point, a persistent beachhead inside your network, operated by your adversaries, using your own trusted infrastructure as cover.
Security investigations have documented compromised edge devices being used to:
- Intercept authentication flows and harvest credentials as they transit the device, before encryption, after decryption, or via session inspection.
- Deploy web shells on internal systems, creating persistent remote access that survives device reboots and standard remediation attempts.
- Create unauthorized accounts with elevated privileges, ensuring persistence even if the initial vulnerability is patched.
- Pivot directly into sensitive infrastructure virtualization platforms, identity systems, and internal administrative consoles — all from a position of implied trust.
- Suppress logging and monitoring activity so that the compromise goes undetected by the very systems designed to catch it.
Real-world incidents reflect these patterns. In documented cases, attackers leveraged compromised F5 BIG-IP devices to move from internet-facing edge infrastructure directly into internal VMware vSphere environments. In separate campaigns, vulnerabilities in Check Point gateway devices were simultaneously exploited across dozens of organizations globally.
Firmware-level implants: the attack that survives everything
The most alarming evolution is firmware-level compromise. In the ArcaneDoor campaign, targeting legacy Cisco ASA devices, threat actors chained multiple zero-day vulnerabilities to deploy a firmware bootkit called RayInitiator. This implant operates below the operating system, meaning it survives reboots, software updates, and factory resets.
Alongside RayInitiator, attackers deployed an in-memory payload capable of capturing authentication traffic and actively suppressing logging. The compromised device simultaneously became the attack platform and the concealment mechanism. When logging is suppressed and monitoring is absent, defenders lose visibility into the intrusion entirely.
Operational relay box networks: your infrastructure as attack infrastructure
State-sponsored threat actors have moved beyond using compromised edge devices solely as entry points. They are repurposing them as nodes in global Operational Relay Box (ORB) networks, routing malicious traffic through legitimate but hijacked enterprise infrastructure. Clusters linked to groups including APT15 and Hafnium demonstrate how these relay networks dynamically rotate attack paths to obscure attribution, making malicious traffic appear to originate from trusted enterprise systems.
The Connection to Identity Compromise
Edge decay and identity-based attacks are not separate problems. They are sequential phases of the same intrusion and edge compromise is increasingly the first step.
Once an attacker controls a gateway or VPN appliance, they gain access to the authentication flows, session data, and credential material transiting that device. From there, they can pivot directly into identity infrastructure — bypassing traditional defenses entirely by operating with valid credentials rather than attempting to break authentication systems.
Attackers don’t need to break your authentication systems if they can intercept your credentials in transit. Edge compromise gives them exactly that position — inside your network, inside your authentication flows, operating as a legitimate system.
Propelex Security Team
This creates a compounding risk: edge compromise enables identity theft, which enables lateral movement, which enables full network access, all using valid credentials that trigger no authentication alerts. The pattern from edge access to identity abuse to full-scale intrusion is now the dominant architecture of sophisticated enterprise attacks.
What Your Organization Must Do Now
Edge decay will not resolve through routine patching alone. The tools available to adversaries are becoming cheaper, faster, and more automated every quarter. Organizations that treat this as a standard vulnerability management problem will continue to lose ground.
- Audit every edge device in your environment. Identify what you have, where it runs, what firmware version it carries, and critically what visibility you have into its activity. Every device outside your monitoring is a potential beachhead you don’t know about.
- Extend monitoring to devices that can’t run EDR. Alternative strategies, network flow analysis, syslog aggregation, behavioral baselining — can provide anomaly detection even for devices that cannot host modern security tooling.
- Accelerate patch cycles for edge infrastructure. Treat edge device vulnerabilities with the same urgency as critical server vulnerabilities. The window between disclosure and exploitation has collapsed from weeks to hours.
- Implement continuous integrity validation. Stop treating edge devices as trusted by default. Regular firmware verification, log integrity checks, and behavioral review processes should be standard, not exceptional.
- Connect edge security to your identity security strategy. Zero trust architecture principles, least privilege, continuous verification, microsegmentation — reduce the blast radius when an edge device is compromised. Edge security and identity security must be designed together.
Defending the modern edge requires moving from device-level alerts to attack lifecycle visibility, and from assumed infrastructure integrity to continuous validation. The perimeter cannot be treated as a reliable line of defense on its own — because in most environments, it no longer is.
How Propelex approaches edge security
At Propelex, we partner with organizations to assess and harden the full attack surface — including the edge infrastructure that standard security tools leave blind. Our Cybersecurity Risk Assessments map every edge device in your environment against current threat intelligence, identify visibility gaps, and prioritize remediation based on real-world attacker behavior rather than theoretical severity scores.
Our Penetration Testing services directly simulate the attack patterns described here — testing whether your edge devices could serve as launchpads for lateral movement, credential harvesting, and identity compromise, and whether your detection capabilities would catch an adversary who had already crossed your perimeter.
For organizations without dedicated security leadership, our Virtual CISO service provides the strategic guidance needed to build an edge security program that keeps pace with a threat landscape that is evolving faster than most organizations can track internally.