Intrusion Detection System 101: Buyer’s Guide 2025

If somebody cut your perimeter fence or forced entry to your premises, how quickly would you know about it? Without an advanced warning system, these breaches can go undetected for too long. The consequences are dire: operational disruption, compliance penalties, and serious loss or damage to property, IP, and profits.

This is why an Intrusion Detection System (IDS) is essential to any modern security strategy. Your IDS is like a diligent team of guards, monitoring your environment for unwanted activity and alerting you to threats before they can develop.

Welcome to your comprehensive buyer's guide for 2025, explaining what an IDS is, key features and different types, how to choose the right solution, and what to avoid.

What Is an Intrusion Detection System?

An Intrusion Detection System (IDS) monitors physical spaces, perimeters, or specific assets for signs of unauthorized entry, presence, or activity. The resulting alerts serve as a crucial early warning system.

Unlike a lock that only prevents entry, an IDS observes, analyzes, and notifies, giving security teams intelligence to help investigate and respond to threats that might otherwise go unnoticed until it’s too late.

Why your organization needs an Intrusion Detection System in 2025

Looking at wider trends in security issues, the need for robust intrusion detection has never been greater.

• An evolving threat: Potential break-ins, vandalism, theft, and spying are constant issues. Whether from targeted sabotage or someone trying their luck, bad actors take advantage of your vulnerabilities and can wreak havoc. Locks alone are not enough. An IDS gives you the visibility you need to truly stay protected in 2025.
• Growing compliance and regulatory demands: The regulatory and compliance market is set to grow from $3.48 billion in 2024 to $9.02 billion by 2032. Both industry regulations and governmental mandates are on the rise, each calling for monitoring, auditing, and rapid incident response. An IDS helps you meet these obligations.
• Protecting people: Out of all your assets, people are some of the most important – and vulnerable. An IDS is a vital line of defense for safeguarding equipment, inventory, blueprints, data centers, and operational technology. Even more importantly, however, it keeps your employees and visitors safe from intruders.

Three key types of Intrusion Detection Systems

There are three main types of Intrusion Detection Systems you should be aware of, with each one serving a different purpose and area of your business:

1. Perimeter Intrusion Detection Systems (PIDS)

PIDS detect intruders at the outer edges of your property. They monitor fences, walls, open grounds, or the space around buildings.

You might see technologies like fiber-optic fence sensors, microwave barriers, taut-wire systems, active infrared (IR) beams, radar/doppler sensors, thermal imaging cameras, buried and ground-based sensors.

They are best for large industrial complexes, critical infrastructure sites, airports, military bases, and data centers.

2. Interior intrusion detection systems

These systems monitor movement or unauthorized entry inside buildings, rooms, or specific secure zones within the perimeter.

Common types include motion detectors (Passive Infrared - PIR or dual-technology), acoustic sensors, vibration sensors, magnetic contacts, and pressure mats.

You’ll often find them in commercial offices, retail stores, warehouses, server rooms, executive offices, and vaults.

3. Digital IDS

An effective IDS is backed-up by systems to monitor digital activity for signs of a breach. That might look like changes to critical files, repeated failed login attempts, unexpected network connections, or abnormal application behavior. 

You have Host-Based Intrusion Detection (HIDS), which alerts you to tampering with specific servers or devices. Network-Based IDS (NIDS), meanwhile, detect attacks on networks. There are also hybrid IDS solutions, which offer both.

Any organization with a network and endpoints should have HIDS, NIDS, or both in place.

Key features to look for in an Intrusion Detection Systems

When choosing an IDS, you’ll want to check it has these essential capabilities:

Real-time monitoring and alerts

A top-tier IDS should send instant, actionable alerts to your security team, allowing for rapid response to active physical threats.

Threat detection and analytics

Far smarter than a simple alarm, a powerful IDS analyses signals for an intelligent view on what’s going on. Modern systems leverage machine learning and artificial intelligence to distinguish between genuine intruders and environmental factors (like animals or weather) to reduce costly false alarms. Common detectors include:

• Signature-based detection identifies patterns like the use of specific cutting tools. 
• Anomaly-based detection flags unusual movement patterns.
• Behavioral analysis compares actions against norms and baselines. 

Integration

A disjointed security system isn’t particularly secure. If your IDS can’t integrate with your existing security tools, you’ll create weak spots.

An IDS should connect with your access control systems, CCTV, and building management systems. This gives you layered and unified security, with powerful event correlation (e.g., an alarm from a door sensor triggers adjacent cameras), and automated responses.

Flexibility

Your chosen IDS should offer flexible deployment options.

Cloud-based solutions provide remote management, scalability, and automatic updates for distributed physical sites.

On-premise solutions offer maximum control over data and customization, which suits highly sensitive infrastructures. Hybrid models are available, too.

Scalability

If your system can’t grow with your business, it risks becoming obsolete quite quickly.

Any scalable system should be able to grow wider, as well as deeper. Scaling across multiple sites is just as important as adding more entry points on your existing site.

You should look for remote access and centralized management capabilities, as these reduce a lot of the work of ongoing management.

Customizable rules and reporting

To prevent unnecessary alerts, choose a customizable IDS and create rules that match your organization's unique environment, locations, and operational hours. 

Robust reporting features will cover you for audits, analysis, and proving ROI.

IDS vs. IPS: what's the difference?

It's common to hear IDS mentioned alongside Intrusion Prevention Systems (IPS). While related, they have a few important differences.

Think of an IDS as a concerned citizen who sees something suspicious and raises an alarm. It detects, analyses, and alerts – but it’s entirely passive.

An IPS is more proactive, like a security guard. When it detects a security event, it takes action to stop the intrusion.

So, when is each system best deployed?

Use IDS when your priority is visibility, logging, and intelligence gathering but you don’t want to risk blocking legitimate personnel or operations by accident.

Use IPS for active, real-time protection against known physical threats in critical areas. Just prepare to accept the (small) risk of false positives in return for increased protection.

For comprehensive defense, use both. An IPS will prevent common threats automatically, reducing the workload for your security team. An IDS, deployed in parallel, will detect more subtle or novel attacks that might bypass the IPS, providing intelligence for incident response and threat assessment. As is so often the case with security, a layered approach produces the best results. 

How to choose the right intrusion detection system in 2025

To choose the right IDS for your needs, consider these important factors alongside your organization-specific requirements:

• Budget: Think about the initial and ongoing cost of ownership, from purchase and installation to maintenance, software updates, and monitoring.
• Compliance: Make sure your chosen system supports your organization's compliance duties.
• Resources: An effective IDS needs regular attention. Check your IT and security teams have the capacity to manage, monitor, and maintain the system effectively.
• Vendor support: Choose a reputable vendor with a proven track record in security solutions. Look for comprehensive support, including setup assistance, training, and ongoing technical help.
• System reliability: A reliable IDS functions consistently, minimizes false alarms, and receives regular updates to address new threats and improve performance.
• Scalability: Your organization's security needs will likely evolve. Choose an IDS that can expand to cover a growing number of physical sensors, as well as new locations and perimeters.
• Adaptability: The system should also integrate with existing and new technologies to counter evolving threats.

Common pitfalls to avoid when buying an IDS

Navigating the IDS market can be complex, and some common issues can lead to costly mistakes. Be wary of these pitfalls when shopping for an IDS:

• Ineffective systems: An IDS that generates irrelevant alerts every time a strong breeze blows or a fox slinks past can lead to alert fatigue. This causes security teams to dismiss warnings, potentially missing real physical threats amidst the noise. Your system needs proper tuning and advanced analytics to minimize this.
• Standalone solutions: If your new IDS can’t talk to your existing physical security tools, can you really rely on it? A standalone IDS creates fragmented security, making it harder to correlate events, verify alerts, and respond effectively to physical incidents.
• Shiny Object Syndrome: It’s tempting to buy the system with the nicest sales pitch. However, overspending on unnecessary features might mean you miss crucial ones that address the actual risks you face. Instead, thoroughly identify your unique risks and vulnerabilities and choose an IDS that best addresses them.
• Non-compliance: Selecting a system that doesn't meet current regulatory requirements will lead to penalties and legal issues.
• Stagnant systems: Choosing an IDS that can't expand as your organization grows, means your choice will quickly become obsolete making it expensive to replace.
• Unmanaged, unmaintained: An IDS is not a ‘set it and forget it’ solution. If you don’t have the trained personnel to monitor alerts, manage the system's rules, perform routine maintenance, and respond to detected physical intrusions you will undermine the system's effectiveness.

Why choose Acre Security for Intrusion Detection in 2025?

Acre Security provides comprehensive intruder detection systems that act as a vital player in your overall security architecture.

Acre's solutions integrate with your existing security ecosystem including physical access control systems, video surveillance, and alarm systems. This gives you a single, centralized view of all security events for faster threat identification and streamlined incident response.

With Acre, you get reliability and scalability as standard. So your intrusion detection capabilities grow with your organization's needs, protecting everything from sensitive data centers to vast industrial complexes and all the physical assets within them.

Learn more about our comprehensive IDS and see how a unified approach can protect your organization from the inside out. 

Defend your premises on time, every time

In an era of sophisticated threats, an Intrusion Detection System is indispensable to robust security strategies. By providing early warning and insights into suspicious activity across your locations, networks, and assets, an IDS helps you proactively defend your organization.

Don't leave your buildings and assets vulnerable to unseen threats. Let’s develop next-level protection for your entire organization.

Contact us today.