Asset Discovery: How to Find Every Device on Your Network

Security teams already know the standard line: they cannot protect the assets that they cannot see connected to their networks. Today’s enterprise networks manage more connected devices than most organizations can count, a problem accelerated by cloud adoption, remote work, and the growing number of connected OT and IoMT devices. For example, according to research from Trend Micro, 91% of respondents acknowledged that attack surface management is either directly or somewhat connected to their organization’s business risk, while 55% have no continuous way to proactively manage this risk. As organizations add more devices to their networks, maintaining an accurate asset inventory that provides visibility into the organization’s attack surface becomes more challenging.

Organizations can no longer manage all their digital assets in a single spreadsheet and assume they have a complete inventory. This blog post will explain why organizations need continuous visibility into their dynamic networks and comprehensive asset management across IT, operational technology (OT), Internet of Things (IoT), and Internet of Medical Things (IoMT) devices. After explaining why, this guide will cover how gaining comprehensive, real-time full device visibility across IoMT, IoT, OT, and IT that maps every device connected to the network builds the foundation for a robust asset discovery and management program. 

What is Asset Discovery?

Asset discovery is the process of finding and identifying every device connected to a network, then keeping that inventory current. The process acts as the starting point for building other security controls, like patching vulnerabilities, segmenting networks, and monitoring devices. 

Today, the phrase “every device” includes:

• Traditional IT endpoints: Windows and Unix servers, laptops, telephones, virtual machines, load balancers, and the software applications and cloud services running across on-premises data centers and cloud environments
• IoT devices: Printers, cameras, badge readers, building controls
• OT: Programmable logic controllers (PLCs), SCADA remote terminal units (RTUs), building automation controllers (HVAC/BAS controllers)
• IoMT: Infusion pumps, patient monitors, medical imaging systems
• IoMT:  Infusion pumps, patient monitors, medical imaging systems

Traditionally, organizations used a static spreadsheet to track their devices, often updating them during an annual audit or after making a purchase. These point-in-time lists rapidly become outdated as the organization adds, replaces, and reconfigures devices regularly. Continuous asset discovery offers organizations an asset inventory that regularly updates itself, identifying new and changed devices as they appear, including shadow IT. 

Why Asset Discovery Matters For Security

Every unknown device connected to an organization’s network is an unmonitored access point that expands the organization’s attack surface. Since attackers target these weak unmanaged devices to gain initial access, attack surface management programs that incorporate asset discovery tools seek to close this coverage gap. Malicious actors scan networks to locate devices that the organization fails to patch and monitor, like unidentified cameras, forgotten test servers with static IP addresses, or unmanaged IoT sensors. When these devices have no owner responsible for patching and monitoring them, they become unmanaged endpoints and an attack risk that weakens the organization’s overall security posture.

Palo Alto, Siems, and the Idaho National Laboratory’s research “Intelligence-Driven Active Defense Report 2026: Securing Operational Technology Environments” found a 332% increase in unique internet-exposed OT devices and services with nearly 20 million OT-related devices observable on the public internet. This exposure translates directly into risk for organizations that believed they had isolated their industrial environments. 

Beyond technical risk, unknown devices can impact operations through:

• Audit findings: Teams may be unable to provide a comprehensive asset inventory when auditors request them, especially when shadow IT devices were never approved or documented, leading to compliance violations. 
• Incident response: Slower investigation times when analysts need to identify an unmanaged device before containing an attacker. 
• Patch management: Vulnerability scans can only run against the devices in their list, which becomes especially difficult for IoT, OT, and IoMT devices that traditional scanners can take offline during the scan. 

When teams incorporate asset discovery into their day-to-day operations, they routinely find 15-30% more devices than they expected. 

Active vs Passive Asset Discovery

For organizations that add IoT, OT, and IoMT devices to their networks, using active asset discovery tools becomes an operational risk as those tools can take fragile devices offline. Many organizations pair them with passive asset discovery tools to capture this missing information.

Active Discovery

With active scanning, the tool probes the network directly, sending queries to devices and reading their responses to identify them, often through ICMP pings, SNMP polling, port scans. This fast process can pull detailed information in a single pass because it communicates directly with the devices. 

However, the speed can create real risks. Some devices, specifically in OT and IoMT environments, were not built to handle unexpected network traffic. While a modern traditional IT endpoint can handle these scans, these communications can take a bedside monitor or PLC offline. In environments where uptime is critical, teams often trade discovery for continued availability. 

Passive Discovery

Passive discovery is essentially an agentless network scanner that watches traffic to identify devices based on their communication patterns, without querying or touching them directly. Unlike a discovery agent installed directly on each endpoint, a passive discovery tool never sends requests to the device, eliminating the potential for disruption arising from the discovery process. 

This agentless, hands-off method is a safer default for any devices that require continuous uptime, like bedside monitors and PLCs. While passive monitoring may collect data more slowly, it removes potential operational risks. 

For sensitive environments like hospitals and industrial plants, passive discovery fits their operational model and service availability requirements. 

How Asset Discovery Works, Step By Step

Understanding how asset discovery works helps highlight why the process is challenging for many organizations. 

1. Collect

Discovery starts by collecting data about devices connected to the network. Most organizations use active scanners that collect information like:

• SNMP polling 
• Port scans
• API calls to switches and controllers
• Integrations with existing systems like Configuration Management Databases (CMDBs), directory services, network access control (NAC) platforms, and cloud platforms queried through their APIs

Passive discovery tools offer organizations two specific benefits. They collect data about IoT, OT, and IoMT devices that would otherwise leave them unmanaged, and they supplement the active discovery tool’s endpoint data with device behavior information. Some information that passive scanners provide includes:

• DHCP requests
• ARP tables
• DNS queries
• mDNS/UPnP broadcasts
• Metadata embedded in normal device chatter

2. Identify & Classify

At the collection stage, an organization captures raw data. Security teams need information that helps them take action. Identification matches device network data to a specific real-world identity. Instead of labeling the device by IP number, the security team knows what specific device make and model they have.

The classification builds on the identification step, turning raw data into a structured record to create real asset intelligence that includes a device identity and details so security teams can make informed decisions about next steps. Classification also matters because different device types carry different risks and require different handling. A printer and an infusion pump have different security and monitoring needs. 

A complete device record at this stage usually includes:

• Device type: The kind of device it is, like workstation, IP camera, PLC, infusion pump,  or HVAC controller
• Make and model: The manufacturer and specific hardware version
• Operating system or firmware: The current version, to identify outdated or end-of-life software 
• Network location: Where the device sits, which segment or VLAN, and what it can reach and how it factors into dependency mapping for the systems around it
• Owner or responsible team: Responsible party for the device, anchored by accurate ownership data across clinical, IT, and OT teams
• Communication behavior: What the device normally talks to and its software usage patterns, forming the behavioral baseline used for spotting anomalies or communications with attacker infrastructure

3. Enrich

A classified device tells security what the device is but fails to provide insight into why it matters or whether leaving it connected creates more risk. Enrichment closes this gap by incorporating context that turns the inventory into actionable asset intelligence, including information like:

• Known vulnerabilities tied to the specific device
• A calculated risk score
• Location on the network
• Network segment
• Neighbors on the network
• Potential attack path
• Business or clinical functions the device supports

Without enrichment, every vulnerability on every device looks equally urgent, leaving responsible parties adrift as they try to remediate all vulnerabilities all the time. By providing this context, security teams can focus on the devices that pose the highest risk, using that impact analysis to reduce the attack surface meaningfully.

4. Monitor Continuously

An asset inventory is almost immediately outdated unless the organization can apply real-time, continuous updates. Networks are dynamic:

• Employees or customers connect their personal devices to guest networks 
• IT teams swap out an old printer for a new one
• Contractors connect their laptops to the internal network to troubleshoot a controller 

Without continuously running discovery, each of these changes leads to an unmanaged device that attackers can exploit. Continuous monitoring watches for three kinds of change: 

• New devices joining the network: Identifying all new devices enables security teams to ensure configurations align to change management expectations and do not impact the overall security posture.
• Existing devices being reconfigured or replaced: Managing configurations and replacements ensures that all changes comply with the organization’s change management and procurement policies. 
• Shifts in how a known device behaves: Detecting behavior anomalies helps identify a potentially compromised device that a malicious actor may be using as part of a botnet.

• Existing devices being reconfigured or replaced: Managing configurations and replacements ensures that all changes comply with the organization’s change management and procurement policies. 
• Shifts in how a known device behaves: Detecting behavior anomalies helps identify a potentially compromised device that a malicious actor may be using as part of a botnet.

Asset discovery must be an ongoing capability rather than a point-in-time project with a start and end date. 

Asset Discovery for IoT, OT, and IoMT Devices

Traditional asset discovery tools focus on traditional IT devices running that”

• Accept an agent
• Tolerate a reboot
• Have a short lifespan

IoT, OT, and IoMT fall outside these traditional parameters. A PLC with firmware from a decade ago may not be able to run an agent or survive an unexpected port scan. A patient monitor in a hospital room must remain online to ensure patient health. Further, these non-traditional devices use various protocols, like Modbus, BACnet, DICOM, HL7, that traditional tools cannot parse, meaning that many of them misidentify or fail to identify them appropriately. 

Deep, agentless profiling solves these problems by fingerprinting the traffic a device already generates using:

• TLS handshake parameters
• HTTP headers
• DHCP options
• Protocol-specific fields

It then matches these patterns against a library of known device signatures to identify make, model, and firmware version without ever sending the device a single packet. The IoT, OT, and IoMT devices become part of the larger inventory without any service disruption. The traditional IT devices gain additional data to enrich the information that the active scanner provides. 

This is exactly the environment Asimily was built for, and it shows in independent evaluation. Asimily was ranked #1 in the 2026 Best in KLAS Healthcare IoT Security report, the industry’s leading independent benchmark for this category. For more on securing the industrial side of this equation, see our guide to OT security.

What To Look For In An Asset Discovery Solution

When looking to invest in an asset discovery solution, these are some questions to consider asking the vendor:

1. Does it discover new devices automatically, without manual intervention?
   As networks are dynamic, organizations need automation that ensures continuous updating.
2. Does it de-duplicate devices seen by multiple sources, so one device isn’t counted twice?
   Deduplication ensures a single finalized entry when multiple tools identify the same device to improve audit outcomes and risk scoring.
3. Can it discover devices without disrupting fragile OT and clinical environments?
   Organizations need tools that they know can prevent IoT, OT, and IoMT devices from restarting, dropping processes, or triggering alarms. 
4. Does it combine passive, agentless discovery with active scanner data, rather than relying on one method alone?
   Passive scanning augments active scanner data and identifies additional device types to create a single source of truth. 
5. Does classification go beyond an IP and MAC address to make, model, firmware, protocols, and patch levels?
   Deep classification ensures all responsible parties can use the inventory for risk prioritization.
6. Does the inventory update in real time as the environment changes, rather than on a periodic scan cycle?
   Real-time updates mitigate risk by ensuring the organization acts on data reflecting the current network status.
7. Does it flag unauthorized, rogue, or shadow devices as soon as they appear?
   If an attacker plants a device or an employee connects without asking, security teams need to know as soon as it joins the network.
8. Can it support compliance frameworks with a defensible, structured taxonomy?
   Auditors and regulators want a structured, defensible taxonomy, so a tool that maps naturally to frameworks saves time when gathering audit documentation.

FAQs Organizations Have About Asset Discovery

1. What is asset discovery?

Asset discovery is the process of finding, identifying, and classifying every device connected to a network, then keeping that inventory current over time. It acts as the first step for a security program, because visibility has to exist before protection can.

2. What is the difference between active and passive asset discovery?

Active discovery probes devices directly and returns results quickly, but the probing itself can disrupt fragile equipment. Passive discovery watches network traffic and identifies devices without touching them, making it the safer choice for IoT, OT, and IoMT environments that require continuous uptime.

3. What are asset discovery tools?

Asset discovery tools are software platforms that automate the work of finding, identifying, and tracking devices on a network. Core capabilities typically include passive traffic analysis, device classification, and risk enrichment, replacing manual spreadsheets with a continuously updated inventory

4. How does asset discovery work?

It follows four general steps: collect signals from network traffic and, where safe, direct queries; identify and classify each device by type, make, model, and owner; enrich that record with vulnerability and risk context; and monitor continuously so new or changed devices are caught as they appear.

5. Why is asset discovery important for cybersecurity?

Organizations cannot protect or patch a device they don’t know exists. Asset discovery is the foundation that visibility, risk reduction, and audit readiness are all built on, and teams that run it for the first time often uncover 15 to 30 percent more devices than they expected.

6. What is agentless asset discovery?

Agentless discovery identifies and profiles devices without installing any software on them. Some devices are unable to run software, like medical devices, OT equipment, and IoT devices. Agentless asset discovery is closely tied to passive monitoring as the underlying method.

7. How is asset discovery different from asset management?

Discovery finds and identifies devices; asset management tracks them over their full lifecycle, including ownership, maintenance, and eventual retirement. Discovery feeds asset management an accurate, live inventory to work from, rather than relying on manual entries.

8. Can asset discovery find IoT and OT devices?

Yes, when the tool is purpose-built for it. Generic IT discovery tools often miss IoT and OT devices entirely, while purpose-built platforms use passive, agentless techniques and deep profiling to identify them accurately, including specialized IoMT devices in clinical settings.

9. How often should asset discovery run?

Modern asset discovery runs continuously rather than as a periodic scan. That matters because new and changed devices show up on networks constantly, and a monthly or quarterly scan leaves a long window where the inventory doesn’t match reality.

10. What is passive asset discovery?

Passive asset discovery identifies devices by observing network traffic, without sending any probes to the devices themselves. Because nothing is sent to the device, it’s the safest method for fragile equipment, and it’s often described as agentless discovery for this reason.

Asset discovery turns an unknown, sprawling network into a mapped and monitored one. When organizations know every device connected to their networks, they can build the rest of their security controls around this information. Getting the process right means matching the method to the environment. Fast active scanning provides immediate answers where running it is safe. Passive, agentless discovery collects information from fragile devices, like IoT, OT, and IoMT, while augmenting the active scanning data. 

The fundamentals to remember:

• See everything first. You can’t secure a device that isn’t in your inventory, so complete visibility across IT, OT, IoT, and IoMT has to come before anything else.
• Go passive for fragile devices. Active scanning can disrupt OT and medical equipment; passive, agentless discovery gets the same visibility without the risk.
• Make it continuous. A one-time inventory goes stale immediately; discovery has to run continuously to keep pace with a network that never stops changing.

Reading about asset discovery only goes so far; the real value shows up once you can see what’s actually connected to your own network. If you’re ready to find out how many devices are hiding in your environment right now, see Asimily on your network with a guided, no-disruption walkthrough tailored to your IT, OT, and IoMT footprint.