The Hidden Risks in Your Network: IoT, Peripherals, and DNS-layer Blind Spots

Shadow IoT and unmanaged peripherals silently expand your attack surface while evading endpoint tools. Learn how DNS filtering restores DNS-layer visibility, stops threats earlier, and why agentless detection of all DNS-active devices delivers full network visibility.

Picture this: You're running a tight ship with your cybersecurity – firewalls running, endpoint detection and response (EDR) agents deployed on every laptop and server. But lurking in the corners of your network are the forgotten ones: that old printer humming in the break room, the IP camera watching the lobby, or the smart lamp someone installed last year. These devices don't play by the same rules. They can't run your fancy security agents, they're rarely patched, and attackers love them for it. In fact, as we hit 2025, reports show that over 50% of IoT devices carry critical vulnerabilities ripe for exploitation, and one in three data breaches now involves an IoT gadget. It's a blind spot that's growing faster than most teams can handle.

But there's also good news, every connected device has to "phone home" using DNS to resolve domain names into IP addresses. By filtering at this layer, you can spot suspicious activity early, block bad connections before they happen, and gain visibility into everything on your network – without installing a single agent on those tricky devices. A strategy that the NSA and CISA have been updating their guidance in 2025 to make protective DNS a go-to for enterprises and governments alike.

In this article, we'll dive into why these hidden risks are so dangerous, how DNS filtering plugs the gaps, and practical steps to implement it.

How Have Peripheral Devices Become a Security “Blindspot”

If you are old enough you probably remember the times when most of the devices were simply what they were made to be. An thermostat would just measure temperatures but now it's a full-fledged computer on your network, complete with its own operating system and internet connection. The same goes for IP cameras, VoIP phones, badge readers, and even smart lights. And while traditional security excel in environments where software deployment is feasible. Most IoT devices being smarter than before are still "headless" in the matter of security as it is still not plausible to support the endpoint detection and response (EDR) agents that protect your laptops.

Industry assessments consistently identify unmanaged devices as high-risk, with vulnerabilities stemming from weak authentication, unpatched firmware, and insecure communications.

According to Forescout’s 2025 report, device risk rose by 15% across IT, IoT, and OT environments, with routers, VoIP devices, and network video recorders among the riskiest connected devices. With the dissolution of traditional perimeters in hybrid environments, adversaries capitalize on these gaps, targeting edge devices for initial access before lateral movement. And network segmentation deficiencies and ransomware targeting OT further exacerbate risks.

Where Did it All Start?

To understand how the Internet of Things (IoT) evolved from a convenience into a persistent cybersecurity liability, it's worth revisiting a pivotal moment in 2016 – the emergence of the Mirai botnet. What began as a crude tool for knocking Minecraft servers offline soon became a global wake-up call for the dangers of insecure connected devices.

Mirai was developed by three college students – Paras Jha, Josiah White, and Dalton Norman. Initially, their goal was simple: disrupt competitors in the Minecraft server business using distributed denial-of-service (DDoS) attacks. But the tool they created would go far beyond that. Named Mirai – Japanese for "future" – the malware targeted internet-connected devices running Linux on ARC processors, commonly found in low-cost routers, IP cameras, and DVRs.

Rather than leveraging zero-day exploits, Mirai used a brute-force dictionary of 61 hardcoded default username-password combinations, credentials like “admin/admin” or “root/12345” that were never changed by users or vendors. Once compromised, devices would be silently enrolled into a botnet, wiping out other malware, connecting to a command-and-control (C2) server, and sitting idle until commanded to attack.

By mid-2016, the botnet had infected hundreds of thousands of devices across the globe. In September, Mirai launched a 620 Gbps DDoS attack on Krebs on Security, the cybersecurity blog run by journalist Brian Krebs. This was widely seen as retaliation for his reporting on DDoS-for-hire services and pushed even major content delivery providers like Akamai to their limits.

But it was the October 21, 2016 attack on DNS provider Dyn that truly signaled a paradigm shift. Mirai unleashed a flood of traffic peaking at 1.2 Tbps, effectively breaking the internet for several hours across the U.S. East Coast. Major platforms: Twitter, Netflix, Reddit, Spotify, and The New York Times – became unreachable, not due to a nation-state cyberwarfare campaign, but because a group of teenagers exploited forgotten gadgets in people’s homes.

The industry response was swift, though not comprehensive. Vendors issued recalls and firmware patches, and regulators began outlining baseline security requirements. For instance, California enacted legislation mandating unique default passwords for IoT devices. A pivotal moment came in October 2016, when Mirai’s source code was released publicly, allegedly to obscure the identities of its creators amid growing scrutiny. This disclosure triggered a proliferation of Mirai variants, many of which are still active as of 2025.

According to reaserches, over 2.6 million IoT devices were compromised in botnet-related incidents in the first half of this year alone, with 61% linked to Mirai or its derivatives. Recent campaigns have exploited vulnerabilities in GeoVision surveillance cameras and unpatched Wazuh systems, proving that the threat remains dynamic and persistent.

Mirai’s enduring legacy lies in its simplicity and effectiveness. It didn’t require advanced techniques, just poor security hygiene and a massive attack surface. It highlighted how billions of unmanaged, unpatched devices could be weaponized at scale, forcing the cybersecurity community to look beyond device-level protections.

Today, network-level controls such as DNS filtering, traffic anomaly detection, and microsegmentation are considered essential in environments containing IoT devices. The shift toward zero trust architectures and continuous monitoring owes much to the lessons learned from Mirai.

Nearly a decade later, the botnet that began as a tool for online gaming dominance still echoes across the internet. Mirai didn’t just break websites, it broke the illusion that IoT could be trusted by default.

Why This Blind Spot Still Exists in 2025

If you operate in real environments, not just in planning decks, you already know why this problem persists. Modern enterprise networks are not centralized infrastructures, they are distributed ecosystems. Devices appear wherever there’s power and connectivity. A badge reader gets installed during a lobby renovation. New AV equipment arrives ahead of a major webcast. A third-party contractor installs security cameras to meet insurance requirements. None of these teams are responsible for endpoint security, and most of the devices they deploy can't support traditional security agents anyway.

From this several issues are created between them are the issue of lifecycle mismatch IT-managed assets like laptops have refresh cycles of 3-4 years. Printers, cameras, digital signage, door controllers, and VoIP handsets are expected to live twice that, sometimes more. We patch endpoints monthly. We patch operational systems when downtime is tolerable, which may be years apart. The result is long-lived, minimally maintained firmware islands that quietly persist across infrastructure refreshes. Supply chain opacity doesn’t help. Many devices are stitched together from SDKs and third-party modules that vendors rarely document. You’ll see a CVE drop for a kernel in a surveillance camera, but you won’t know if your hardware revision is affected until a forum post shows up or the vendor quietly slips a new image in the portal. Meanwhile, the device is humming along on a flat network because it “just needs to reach the cloud,” and nobody can tell you what that cloud actually is.

Then there’s ownership. Who “owns” a printer’s security posture? IT Operations? The line of business that bought it? The managed print provider? On paper it’s a team effort. In practice, it’s a juggler’s act, until an incident makes it everyone’s problem at once.

Finally, encryption is a double-edged sword when it’s pointed the wrong way. Encrypted DNS (DoH/DoT) is great for privacy and integrity, but if applications send it to a public resolver you didn’t pick, you’ve just lost visibility and policy enforcement. Put all of that together and you get a stubborn class of hidden network threats: devices you can’t easily patch, can’t conveniently segment, and can’t instrument with EDR. They’re still part of your attack surface, whether you like it or not.

DNS Filtering and the Advantages of Agentless Detection

DNS-based security provides a foundational advantage in managing and protecting modern enterprise networks, particularly those with a high volume of unmanaged or IoT devices. One of the key strengths of DNS filtering lies in its ability to deliver agentless visibility and policy enforcement across all DNS-active endpoints. Regardless of how minimal, appliance-like, or “headless” a device may appear, if it initiates outbound communication using hostnames, it must first resolve those hostnames via DNS. This requirement creates a universal signal, DNS traffic, that can be monitored and analyzed for security insights.

Protective DNS (PDNS) solutions capitalize on this inherent behavior. By directing DNS traffic to resolvers that provide domain classification, policy enforcement, and detailed logging, organizations gain a powerful tool for both prevention and visibility. A robust PDNS service typically provides the following capabilities in real time:

● Threat Prevention: Blocks access to known malicious domains, including malware command-and-control (C2), phishing infrastructure, typo-squatted domains, and staging servers, before any network session is established.

● Anomaly Detection: Identifies suspicious or unexpected behavior, such as newly registered domains, algorithmically generated hostnames (DGAs), or destination categories that are inconsistent with the device's intended function.

● Inventory and Attribution: Logs each DNS request with precise timestamps and source identifiers, effectively turning the resolver into a passive asset discovery mechanism. This enables continuous, real-time identification of DNS-active devices across the network without requiring endpoint agents.

The third capability, agentless device detection, is often undervalued. Traditional inventory systems like CMDBs or NAC platforms can suffer from outdated data or unreliable fingerprinting. DNS logs, by contrast, provide direct evidence of activity: if a device is powered on and communicating, it will generate DNS queries. This approach offers comprehensive, real-time visibility without requiring additional software deployment or integration complexity.

In essence, DNS security isn't dependent on complex new technology, it’s an effective application of existing infrastructure. When used strategically, DNS becomes more than a naming service, it becomes a control point for visibility, threat mitigation, and asset awareness.

IoT Policy Best Practices

Securing Internet of Things (IoT) devices is critical in today’s connected world, where vulnerabilities can expose networks to significant risks. Below are key best practices to safeguard IoT devices, ensuring robust protection against evolving threats:

● Change Default Credentials: Replace factory default usernames and passwords with strong, unique credentials to prevent unauthorized access.

● Keep Firmware and Software Updated: Regularly apply patches and updates to fix security vulnerabilities. Enable automatic updates where possible.

● Secure Wi-Fi: Use WPA3 (or WPA2 if WPA3 is unavailable) with a strong password for Wi-Fi networks.

● Segment Networks: Place IoT devices on a separate VLAN or network to isolate them from critical systems.

● Disable UPnP: Turn off Universal Plug and Play to prevent automatic network configuration by attackers.

● Enable Encryption: Ensure all data transmitted to and from IoT devices uses strong encryption protocols (e.g., TLS 1.3) to protect against eavesdropping.

● Control DNS Traffic: Permit only DNS over HTTPS/TLS to your enterprise resolver, block UDP/TCP port 53, and restrict devices to resolve only necessary domains.

● Encrypt to yourself, not to the world. Encrypted DNS is good, but only when it terminates at your enterprise resolver. Otherwise you’ve traded surveillance risks for operational blindness. Block alternate resolvers and application-level DoH that detours around policy.

● Use multi-factor authentication (MFA) for device access where supported, and avoid sharing credentials across devices or services.

● Disable Unnecessary Features: Turn off unused features (e.g., remote access, microphones) to minimize attack surfaces.

● Secure Physical Access: Prevent tampering by placing devices in secure locations and using tamper-resistant hardware when possible.

● Choose devices from reputable manufacturers with a history of providing security updates.

● Monitor and Log Activity: Stream DNS and device logs to a SIEM system, alerting on anomalies like high-volume TXT queries or suspicious domain resolutions.

Closing Perspective

We’ve been telling ourselves for a decade that IoT will “grow up” and become manageable. Some of it has. Most of it hasn’t. The reality is simpler: these devices aren’t going to adopt your EDR agent, they’re not going to ask before they update their firmware, and they’re not going to raise a hand when their vendor changes cloud providers. They’re going to do what they were built to do, and they’re going to ask DNS for directions while they do it.

That’s our opening. If you put DNS security for IoT at the foundation, encrypting to a resolver you control, blocking detours, and treating the logs as a living inventory, you stop a broad class of problems before they become traffic, and you finally see the edges of your network for what they are. That’s the kind of DNS-layer visibility that turns “we hope our segmentation is good enough” into “we know what this device does, and we can prove it.”