In the early days of networking a firewall plus antivirus software was all you needed. In fact, it was all there was. Now, however, effective network security generally requires the use of a range of tools. This means it can get very confusing, especially to people not involved with it regularly. With that in mind, this article will answer the common question “What is an IDS?” and explain its role in network security.
The most basic answer to the question “What is an IDS?” is that it is an intrusion detection system. A more comprehensive answer to the question “What is an IDS?” is that it is a system for monitoring traffic within a network. When an IDS identifies suspicious activity, it raises an alert. Another security tool and/or a human administrator then takes charge of responding to that alert.
Often, when people ask “What is an IDS?”, they actually mean “What role does an IDS play in the overall network security ecosystem?” That being so, here is an overview of how an IDS connects and cooperates with other key network security tools.
VPNs establish encrypted tunnels for secure data transmission. An IDS monitors the traffic within these tunnels, ensuring that encrypted communication remains free from suspicious activities.
Firewalls sit at the perimeter of a network whereas an IDS sits within the network. In other words, the IDS sits behind the firewall. This means that the firewall does the first triage of traffic based on security policies.
The IDS then does a more robust evaluation of the traffic using more sophisticated detection methods.
Signature-based detection: This compares observed network or system activities against a database of predefined signatures or patterns associated with known cyber threats. It is effective for detecting known threats with established signatures.
Anomaly-based detection: This focuses on identifying deviations from established baselines or normal behavior within the network or system. It is therefore capable of identifying threats without established signatures such as zero-day attacks.
Heuristic-based detection: This involves identifying patterns or behaviors that may indicate a potential threat based on general rules and algorithms. It enables the detection of novel attack patterns without relying on specific signatures.
Behavioral-based detection: This observes the typical behavior of users, systems, or networks and triggers alerts when deviations from the norm are detected. It therefore creates a robust defense against subtle and persistent threats.
Network behavior analysis: This monitors and analyzes patterns in network traffic to detect unusual or suspicious behavior that may indicate a security threat. It provides a holistic view of network activities for comprehensive threat detection.
The intelligence gathered from these more sophisticated detection methods can then be fed back to the firewall and used to update its security policies. This creates a more robust perimeter defense.
Some organizations choose just to use either an IDS or an IPS. Many, however, choose to use both. In fact, there are now “next-generation firewalls” that combine the functionality of a firewall and IDS and an IPS. For some organizations, these can be a more efficient option than running the three tools separately.
An IPS works in almost exactly the same way as an IDS. From a functional perspective, the only difference between IDS and IPS is that IDS is purely used for monitoring traffic. It does not have any reactive capability. By contrast, an IPS can react to a perceived threat. Like a firewall, it can apply pre-defined rules to defend against potentially malicious traffic.
A technical difference between IDS and IPS is that IDS sits outside the flow of traffic whereas IPS sits within it. In other words, IDS is sent a copy of network traffic to analyze. IPS analyzes the actual traffic.
This means that IDS and IPS can work simultaneously without interfering with each other. For practical purposes, this means that IPS can take immediate action to neutralize a threat while IDS raises the alarm about it.
IDS monitors network and system activities for abnormal patterns, deviations, or signs of potential intrusions, providing a broader view of cybersecurity threats. Antivirus software specializes in identifying and removing malicious software, including viruses, worms, and other forms of malware.
IDS alerts can provide valuable context to antivirus software by highlighting potential entry points or compromised systems. Likewise information from antivirus scans can enhance IDS by confirming or providing additional details about detected malware activities.
IDS generates alerts and logs based on detected network anomalies or potential intrusions. These IDS logs are forwarded to the SIEM system, providing a centralized repository for security event data. This enables detailed forensic analysis during incident response, aiding in identifying the root cause of security incidents.
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