Host-Based Intrusion Detection Systems: Everything You Need To Know

Your firewalls and network-level defenses prevent unauthorized remote access, but what happens if an intruder breaks in and compromises a device in-person? Without visibility into individual devices, a breach could go undetected for months. The impacts on your data, operations, and compliance could be extreme.

This is why Host-Based Intrusion Detection Systems (HIDS) are so popular. HIDS is a layer of security and visibility in your computers, servers, and other connected endpoints. Just learning about HIDS or need a refresher? This article has you covered, explaining what HIDS is, how it works, its advantages and limitations, and features to look out for. We also compare HIDS to its network-based counterpart and give you the big picture of how it fits into modern security strategies.

Let’s step into the world of HIDS and learn how it can keep your business safe.

What is a Host-Based Intrusion Detection System (HIDS)?

A Host-Based Intrusion Detection System (HIDS) is a software application installed onto an individual computing device, such as a server or workstation. Unlike systems that monitor network traffic, HIDS focuses inward. Its job is to examine the internal activities of a host device for signs of suspicious or malicious behavior.

How HIDS works: core functions and detection capabilities

HIDS works like a security guard, continuously patrolling a host's internal environment to detect unauthorized access or abnormal behavior. Its core functions include:

File Integrity Monitoring (FIM)

FIM tracks changes to system files, configuration files, executable programs, and other sensitive data.

After establishing a baseline, it will detect when files are modified, deleted, or created. If it doesn’t match an expected pattern, the HIDS notifies security personnel. This is great for tracking events like malware installation, unauthorized software updates, or tampered devices. The best systems will record who made the change and what content was altered.

Log file analysis and suspicious activity detection

HIDS monitors system, application, security, and authentication logs. It looks for patterns that might suggest a threat, such as:

• Abnormal application behavior.
• Repeated failed login attempts.
• Unusual privilege escalation attempts.
• Suspicious process creations or terminations.
• Unexpected network connections originating from the host.

By correlating events across multiple logs, HIDS can identify subtle malicious activities that might otherwise go unnoticed.

Behavior and policy violation alerts

HIDS establishes a normal behavioral baseline for a host or account holder. Any deviation from this baseline triggers an alert.

For example, an account holder accessing protected files for the first time or an application attempting to connect to an unusual external server. HIDS also enforces security policies, alerting administrators to any actions that violate predefined rules, such as attempts to disable antivirus software or change security settings.

Real-time versus periodic scanning

HIDS has two scanning modes: real-time and periodic.

Real-time monitoring continuously scrutinizes activity, providing immediate alerts as suspicious events occur. This is crucial for rapid response to active threats.

Periodic scanning involves scheduled checks and analysis, catching changes that have occurred since the last periodic scan. This is most useful for identifying long-term change patterns.

Comprehensive HIDS solutions offer a combination of both methods.

HIDS vs. NIDS: what’s the difference?

Host-Based Intrusion Detection Systems and Network-Based Intrusion Detection Systems (NIDS) are both vital components of an overall security strategy, but they are distinct from each other. Together, they perform two complementary jobs:

HIDS focuses inward, monitoring individual devices. It sees what's happening inside a specific host, including system calls, internal processes, file modifications, and local log data. Imagine it as having a security camera inside each room.

NIDS focuses outward, monitoring network traffic. It scrutinizes the data traversing the network to detect suspicious patterns that might indicate attacks. It's more like having a security camera watching hallways and doorways.

Neither HIDS nor NIDS is a standalone solution. To offer meaningful protection to your systems, you would ideally use both together.

Benefits of using a Host-Based Intrusion Detection System

Implementing a HIDS can help secure your organization in numerous ways, from the obvious to some more surprising ones.

Visibility

HIDS provide an unparalleled level of detail about what's happening inside an endpoint. Unlike network-based tools that only see traffic, HIDS identify specific actions and processes within systems.

This insight is invaluable for understanding the source and scope of any breach.

Threat detection

One of the real strengths of HIDS is their ability to detect threats within your organization.

Most organizations prioritize protecting their IT systems from outside threats, but there is a clear and obvious risk internally, too. It doesn’t matter if an account holder is misusing their privileges or if their device has been tampered with – you need to know about that activity.

HIDS also identify Advanced Persistent Threats (APTs). This sophisticated malware might bypass traditional perimeter defenses like firewalls or go undetected by antivirus software. By monitoring internal system calls and suspicious activity, HIDS offer an additional layer of defense against the most stealthy attacks.

Compliance

Many regulatory frameworks mandate strict controls over system integrity, data access, and auditing. HIDS provide the detailed logs and audit trails necessary to demonstrate compliance, making audits smoother and more comprehensive.

Customization

HIDS allow security teams to create highly specific rules and policies tailored to the unique behavior patterns expected on a particular host or for certain applications.

This customization helps reduce false positives, ensuring that security personnel only respond to genuine threats or significant deviations from normal operational patterns.

Affordability

Compared to large-scale network monitoring hardware, deploying HIDS agents on endpoints can be a more accessible and cost-effective way to enhance internal security, especially for organizations with limited budgets.

Limitations and challenges of Host-Based Intrusion Detection Systems

The merits of HIDS are clear, but these systems are not without their challenges:

• Resource use: Since HIDS agents run directly on the endpoints, they consume some of the host's processing power, memory, and storage. In resource-constrained environments or on very busy servers, this can reduce performance.
• Alert fatigue: HIDS generates a vast amount of data. Distinguishing truly malicious events from legitimate activities can be challenging. Alert fatigue sets in when a team is constantly turning off false alarms and misses the critical moment of a real threat.
• Issues at scale: Deploying, configuring, and maintaining HIDS agents across a large number of endpoints can be complex and resource-intensive. Keeping your policies, rules, and alert processes consistent – across hundreds or thousands of devices – is a major undertaking.
• Constant maintenance: To remain effective against evolving threats, HIDS relies on up-to-date threat intelligence and continuously refined rules. This needs ongoing effort from security teams to manage signatures, adjust baselines, and tune policies.
• Not guaranteed: It’s possible for particularly skilled attackers to disable or tamper with the HIDS agent itself, rendering it ineffective. Layered security helps mitigate this by having other systems detect such tampering.

Use cases for Host-Based Intrusion Detection Systems

HIDS performs at its best when you need deep endpoint visibility:

Securing sensitive servers

For servers holding highly confidential data (e.g. financial records or employee records), HIDS provides an essential layer of monitoring.

Detecting unauthorized attempts to access or change these sensitive files, even by account holders with some level of legitimate access, is vital for any organization.

Monitoring legacy systems

Older systems or specialized environments (often found in industrial plants or critical infrastructure sites) might not support modern network security tools or antivirus software.

HIDS can provide security monitoring on these endpoints, flagging any unauthorized changes or suspicious processes.

Supporting regulatory compliance

Many compliance frameworks require strict auditing, file integrity monitoring, and detailed logging. HIDS helps meet these mandates by providing verifiable records of host activity and policy violation alerts.

Detecting Advanced Persistent Threats (APTs)

APTs often involve stealthy, long-term compromises. HIDS excels at detecting the subtle, internal movements and changes that characterize these threats, such as unusual file modifications, new process creations, or attempts at privilege escalation on a compromised machine.

Protecting critical infrastructure

In industrial control systems or Supervisory Control and Data Acquisition (SCADA) environments, HIDS monitor the integrity of control systems and alert to any unauthorized tampering that could impact operations.

Key features to look for in a HIDS solution

When shopping for HIDS, you’ll need to find a system suitable for the size, industry, and specifics of your organization. On top of those unique features, you should also check for these hallmark features of quality HIDS:

• Real-time alerts and analysis: The ability to immediately detect and report on suspicious activity. To make sense of vast amounts of host data, the HIDS should provide log analysis.
• File Integrity Monitoring (FIM): Strong FIM offers detailed tracking of changes to critical system and application files, along with who, what, and when information.
• Integration: For faster incident response, a HIDS should seamlessly integrate with Security Information and Event Management (SIEM) systems via centralized dashboards. This allows you to correlate HIDS alerts with data from other security tools (NIDS, firewalls, access control, CCTV, alarm systems).
• Custom rules and policies: To reduce false positives and accurately detect relevant threats, your HIDS needs the flexibility to create and fine-tune rules specific to your organization's environment, applications, and compliance requirements.
• Lightweight deployment and management: The HIDS should have a minimal impact on host performance. To scale the solution alongside your business, you need easy deployment, configuration, and remote management capabilities.
• Automatic updates: To stay ahead of new attack techniques, your HIDS should automatically update rules and signatures based on the latest threat intelligence.
• Automated responses: Some advanced HIDS solutions initiate automated responses to detected threats, such as isolating a compromised host from the network or terminating malicious processes.

Why choose Acre Security for Host Based Intrusion Detection?

Acre Security provides robust host-based monitoring as a vital layer in your overall security architecture.

Acre's solutions detect subtle internal threats that might bypass other defenses as they happen. Our software connects directly with physical access control systems, video surveillance, and alarm systems for a single, centralized view of all security events.

Combined with timely alerts and advanced analytics you’re guaranteed faster threat identification and streamlined incident response. Our systems are reliable at scale, ensuring that your capabilities grow with your organization's needs.

Ready for deeper visibility into your endpoints and stronger internal security? Explore our layered intruder detection systems. 

Spot what other security tools miss

In an era of sophisticated threats, Host-Based Intrusion Detection Systems are an indispensable component of any robust security strategy. By providing granular detail for each endpoint, HIDS helps you spot compromised machines, internal threats, and subtle malicious activities that you’d otherwise miss.

When integrated into your broader security architecture, HIDS provides another layer of awareness, response, and compliance.

Don't leave your critical systems vulnerable to unseen threats: contact us for a no-obligation conversation about your security.