What Are Hosts in Cybersecurity?

A host is any device connected to a network that can send or receive data. That's it. Simple as that.

Your laptop. Your phone. A printer in your office. A server sitting in a data center in Frankfurt. A smart thermostat in your living room. All of these are hosts — because they all have a network address (typically an IP address) and can communicate over a network.

The term comes from early computing, when "host" referred to the main computer that other terminals connected to. Today, it's broadened to mean any addressable device on a network.

Examples of hosts:

• Desktop and laptop computers
• Smartphones and tablets
• Web servers and database servers
• Routers and switches (yes, network devices themselves can be hosts)
• IoT devices (smart cameras, smart locks, industrial sensors)
• Virtual machines (VMs) — even virtual devices count

Why Do Hosts Matter in Cybersecurity?

Here's the thing: every host is a potential entry point for an attacker.

When a hacker wants to break into a company's network, they're not just attacking "the network" in some abstract sense. They're attacking specific hosts — a laptop with weak credentials, an unpatched server, a misconfigured IoT device, whatever gives them a foothold.

This is why so much of cybersecurity is about host security — hardening individual machines, monitoring what they're doing, and detecting when something goes wrong.

According to the NIST Cybersecurity Framework, understanding and managing your assets (which includes hosts) is the very first function of a solid security program. You can't protect what you don't know exists.

Types of Hosts in Cybersecurity

Not all hosts are equal when it comes to risk. Here's how security professionals typically think about them:

1. End-User Hosts (Endpoints)

These are the devices regular employees use every day — laptops, desktops, mobile phones. They're often the weakest link because humans use them and humans make mistakes. Phishing attacks, malware downloads, and credential theft usually start here.

This is why endpoint detection and response (EDR) tools exist. Specifically to monitor and protect these hosts.

2. Servers

Servers are hosts that provide services to other hosts. A web server hosts a website. A database server stores data. An authentication server (like Active Directory) controls who can log in to what.

Servers are high-value targets. Attackers love getting access to a server because it often means access to a lot more than just one machine.

3. Network Infrastructure Devices

Routers, switches, firewalls — these are hosts too, even if they're often overlooked. Compromising a router, for example, can let an attacker intercept all traffic passing through it. There have been several high-profile cases of nation-state actors specifically targeting network devices for exactly this reason, as detailed in CISA Advisory AA23-059A.

4. IoT Devices

Smart cameras, industrial control systems (ICS), medical devices — the Internet of Things has exploded, and most of these devices have terrible security. They often run outdated firmware, have default passwords that nobody changes, and aren't monitored closely.

The 2016 Mirai botnet attack is a perfect example of what happens when IoT hosts are ignored. Attackers compromised hundreds of thousands of cameras, smart TVs, radios with default credentials and used them to launch one of the largest DDoS attacks ever recorded, taking down major websites including Paypal, Netflix, and Amazon. 

5. Virtual Machines and Cloud Instances

In modern environments, a "host" might not even be a physical device. Virtual machines, containers, and cloud instances (like AWS EC2 or Azure VMs) are all hosts from a security perspective. They have IP addresses, they run software, and they can be compromised.

How Attackers Target Hosts

Understanding what hosts are is only half the picture. You also need to know how they get attacked.

Reconnaissance

Before attacking, hackers find out what hosts exist on a network. Tools like Nmap — a widely used open-source network scanner — let attackers discover live hosts, open ports, and running services. This is often the first step in any penetration test or real attack.

Exploitation

Once they identify a host, attackers look for vulnerabilities — outdated software, misconfigured services, weak passwords. This can be done manually by the attacker or a vulnerability scanner like Nessus or OpenVAS can reveal what's exposed. 

Lateral Movement

After compromising one host, attackers often try to move to others. This is called lateral movement. They use the compromised host as a stepping stone to reach more valuable targets — like a finance server or a domain controller.

This is why network segmentation matters so much. If your entire network is flat (all hosts can talk to all other hosts freely), one compromised laptop can become a full network breach.

Persistence

Attackers don't always want to just grab data and leave. Often, they want to stay. They'll install backdoors, create new user accounts, or abuse legitimate remote access tools to maintain access to a host long-term. This is called persistence.

The average time between a breach occurring and it being detected was 181 days in 2025, according to IBM's Cost of a Data Breach Report. That's six months of an attacker sitting inside your network.

How Security Teams Protect Hosts

Now the good stuff — how do defenders fight back?

Host-Based Firewalls

Unlike network firewalls that protect the perimeter, a host-based firewall runs directly on the device and controls what traffic that specific host can send and receive. Windows Firewall and iptables on Linux are classic examples.

Antivirus and EDR

Traditional antivirus looks for known malware signatures. Modern EDR tools go further — they monitor host behavior in real-time, looking for suspicious activity even if the malware has never been seen before. Traditional methods are quite ineffective these days.

Patch Management

A huge percentage of successful attacks exploit known vulnerabilities that already have patches available. Keeping hosts updated is boring, unglamorous work — but it's one of the most effective things you can do. The 2017 WannaCry ransomware attack infected hundreds of thousands of hosts worldwide, most of which were running Windows systems that hadn't applied a patch Microsoft had released two months earlier, as the NCSC confirmed in their official statement.

Log Monitoring

Every host generates logs — records of what happened: logins, file access, network connections, errors. Security teams collect these logs into a SIEM (Security Information and Event Management) system and look for signs of compromise. A host suddenly sending gigabytes of data to an unfamiliar IP address at 3am is a red flag.

Hardening

Hardening means reducing a host's attack surface. Remove software you don't need. Disable services that aren't being used. Change default passwords. Apply the principle of least privilege — accounts should only have the permissions they actually need. The Center for Internet Security (CIS) publishes detailed benchmarks for hardening specific operating systems and applications, and they're completely free to use.

Host Discovery: How Security Teams Find What's on Their Network

You can't protect hosts you don't know exist. This is a real problem — especially in large organizations where devices get added and removed constantly.

Asset discovery is the process of finding all hosts on your network. Companies should maintain a good inventory of their assets to aid proper management and accountability.

The goal is to maintain an up-to-date inventory of every host — what it is, what it runs, who owns it, and whether it's been patched.

A Quick Note on the Term "Host" vs "Endpoint"

You'll often see these two terms used interchangeably, and honestly, in most conversations that's fine. But there's a subtle distinction worth knowing:

• Host is the broader, more technical term — any networked device, including servers, infrastructure, and virtual machines.
• Endpoint typically refers specifically to user-facing devices — laptops, desktops, phones. It's a more business/security-product oriented term.

So all endpoints are hosts, but not all hosts are endpoints. A database server sitting in a rack with no keyboard attached is a host, but most people wouldn't call it an endpoint.

Why This Matters for a Cybersecurity Career

If you're studying for a security certification or trying to break into the field, hosts are everywhere in what you'll learn:

• CompTIA Security+ covers host hardening and endpoint security
• OSCP covers host discovery and exploitation techniques
• CISSP covers asset management, which starts with understanding what hosts you have
• Blue team work (SOC analysts, incident responders) revolves around monitoring and investigating host activity

Understanding hosts is foundational. It's the ground floor of network security. Before you can understand firewalls, IDS/IPS, SIEM, threat hunting, or incident response — you need to understand what a host is and why it matters.

Summary

Let's wrap it up:

• A host is any network-connected device with an IP address — computers, servers, IoT devices, VMs, and more
• Every host is a potential target for attackers
• Attackers target hosts through reconnaissance, exploitation, lateral movement, and persistence
• Defenders protect hosts through firewalls, EDR tools, patch management, log monitoring, and hardening
• Asset discovery — knowing what hosts exist — is the starting point of any good security program

The next time someone asks you "what are hosts in cybersecurity," you'll have a real answer. Not just "a computer thing" — but a clear, grounded understanding of one of the most fundamental concepts in the field.

Found this helpful? Consider sharing it with someone getting started in cybersecurity. Also subscribe to our newsletter below so you get updated when we publish similar content.