The Importance of Host-Based Intrusion Detection Systems

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

A host-based intrusion detection system, or HIDS, is a network application that monitors suspicious and malicious behavior, both internally and externally.

The HIDS’ job is to flag any unusual patterns of behavior that could signify a breach. By bringing this activity to the team’s attention, the HIDS enables in-house staff to investigate and block nefarious activity before serious consequences occur.

“Host-based” refers to the fact that HIDS only monitors and detects across host machines – not the network, which it only uses as a data source. Those host machines include endpoints such as laptops, servers, mobile devices, and any other machine that produces observable data.

The 3 Steps of HIDS

Here’s how HIDS works within an ecosystem:

1. Configuration | IT Admins can take advantage of the predefined rules within HIDS or create their own. These rules define how HIDS will scan log files, and those that come standard are designed to spot common indicators of attack.
2. Detection | Once set up, HIDS looks for anomalous patterns of behavior.
3. Logging and Alerting | It then logs the findings and reports the potentially malicious behavior to your in-house team.

Signature vs. Anomaly-Based HIDS

Host-based intrusion detection systems can work in the following ways or by combining the two approaches.

1. Signature-based | The intrusion detection system (IDS) spots known threats as held and updated in a database. If the database is properly curated and up to date, this method works well at spotting known bad. However, with attackers spinning up emerging threats every day, this approach has obvious weak spots.
    
2. Anomaly-based | Machine learning is used to identify malicious patterns and compare them against established baselines of good behavior. While this does run the risk of more false positives, it also helps organizations spot telltale signs before an attack. While it does lend itself to more false positives, it also enables teams to stop attacks in progress and spot never-before-seen exploits.

HIDS vs. NIDS

To lay the groundwork, intrusion detection systems (IDS) alert security administrators when malicious packets enter the network. Within the IDS category, there are two types:

• Host-Based IDS (HIDS) | A host-based intrusion detection system gets installed on an endpoint and monitors the traffic behavior going to and from that endpoint. It can also monitor attempts to overwrite critical files. HIDS is employed in companies with larger networks and is the more versatile of the two, although it also requires more training and administration than NIDS.
• Network-Based IDS (NIDS) | A network-based intrusion detection system is a standalone solution that detects known and unknown bad across the network. While it does deploy hardware sensors and software on various machines throughout the network, its main focus is on monitoring network traffic, not on protecting individual hosts or devices throughout the enterprise.

Essentially, the two vary in scope. NIDS scans primarily for network-based threats, while HIDS provides deeper insights into internal threats on specific hosts via the recorded logs of endpoint devices. Which one an organization chooses will depend on where they need to bolster their security strategy and their current network size. For some smaller organizations, NIDS alone can make do. However, for enterprise-level teams, HIDS provides the kind of detailed analysis desirable for a granular, defense-in-depth approach to securing internal assets via the network’s endpoints.

Where to Use a Host-Based Intrusion Detection System

Here are some scenarios you might find HIDS in use:

• Data centers, protecting critical infrastructure and servers.
• Endpoints, defending individual devices against malware and insider threats.
• Cloud architecture, providing additional insight into virtual instances.
• Incident response, alerting teams of behaviors that could signify a potential attack.
• Compliance, helping teams meet data privacy and security standards by keeping a running log of host activity.

The Value of a Host Intrusion Detection System

The benefits of using HIDS include:

1. Detailed endpoint data for analysis | HIDS keeps records of user login attempts, file changes, and running processes so analysts can access a revealing swath of endpoint activity.
2. Real-time alerts | When HIDS detects an inconsistency, administrators are flagged immediately so they can take the swiftest corrective action.
3. File integrity monitoring | As HIDS consistently probes for unauthorized file alterations, things like malware and unwanted changes are detected and recorded.

The main value-add of a host-based detection system is that it can quickly and automatically scan endpoint-generated log files once they’re compiled. This leads to all other benefits, and yet this feature alone saves human analysts countless hours scouring logs for hard-to-find anomalies. In addition, HIDS allows users to search the log files more efficiently than they would on their own, as teams can filter by data, application, or other criteria. In some cases, host-based intrusion detection systems can respond to incoming threats automatically, such as by triggering firewall rules.

For organizations looking for in-depth control and visibility over endpoint-based threats, a host-based intrusion detection system provides a way to automatically reference historical behavior, check for anomalies, and identify threats originating on network devices while there is still a chance to stop them.