What is an IDS (Intrusion detection system)?

An Intrusion Detection System (IDS) in cybersecurity is a tool that monitors for suspicious or unauthorised activities on networks, systems, and applications. Its core purpose is to find any potential security breaches, policy violations, or cyber attacks, and create alerts to help security systems deal with them quickly and efficiently.

This guide will cover: 

• What is IDS in cybersecurity? 
• Types of IDS 
• How do intrusion detection systems work? 
• Intrusion detection system examples 
• IDS protection benefits
• Challenges of intrusion detection systems
• IDS evasion techniques
• Things to consider when choosing an IDS 
• IDS implementation best practices 
• FAQs 

What is IDS in cybersecurity?

Intrusion Detection Systems (IDS) are security technologies designed to monitor and analyze data packets and network traffic to identify potential security breaches or intrusion attempts. 

At its core, an IDS will identify two main types of activities: 

• Malicious attacks: Deliberate attempts to exploit vulnerabilities or gain unauthorized access to systems.
• Policy violations: Activities that violate predefined security policies or acceptable usage guidelines.

Types of IDS (intrusion detection systems)

Different types of IDS in cybersecurity focus on different parts of the IT environment. Overall, an IDS can be classified into two main categories, let’s explore them in greater detail. 

Network-Based IDS (NIDS)

• Deployed at specific points within a network infrastructure, typically at network gateways or within segments.
• Analyzes network traffic in real-time, monitoring packets as they traverse the network.
• Uses various techniques, such as signature-based detection, anomaly-based detection, or behavior-based detection, to identify suspicious patterns or known attack signatures.
• Generates alerts that can be further analyzed or trigger immediate response actions.

Host-Based IDS (HIDS)

• Resides directly on individual hosts or servers to monitor activity on the specific system where they are installed.
• Focuses on the activities and behaviors of the host itself, rather than analyzing network traffic.
• Monitors system logs, file integrity, registry changes, and other host-specific events to identify potential intrusions or policy violations.
• Provides granular visibility into individual systems.
• Detects both internal and external threats that may not be captured by network-based monitoring alone.

Other types of IDSs

Within NIDS and HIDS, you can also find a range of intrusion detection systems that have different deployment, detection methods, and functionality. For example: 

• Signature-based IDS: Detects and alerts on threats using pre-defined signatures or patterns of known attacks.
• Anomaly-based IDS: Raises alerts when it detects an activity that deviates from the baseline of normal behavior.
• Heuristic-based IDS: Uses rules and patterns to identify potential threats. They look for deviations from established norms or attack patterns.
• Behavior-based IDS: Monitors application, system, and user behaviour to detect anomalies and signs of possible threats.
• Hybrid IDS: Combines multiple detection methods to strengthen the accuracy and effectiveness of intrusion detection.

How do intrusion detection systems work?

An IDS system in cybersecurity generally uses the following process to identify intrusions:

1. Data collection: IDS collect data from multiple sources, such as network packets (NIDS) or host activities (HIDS). 
2. Traffic analysis: In the case of NIDS, the captured network traffic is analyzed in real-time or offline. It looks for suspicious patterns, using signature-based, anomaly-based, or behavior-based techniques.
3. Alert generation: when an intrusion detection system detects a potential intrusion or suspicious activity, it generates alerts in the form of log entries, email notifications, or SIEM integrations.
4. Incident response: security teams analyze the data, assess the impact, and take action.
5. Continuous monitoring and updates: IDSs must be updated with new signatures and threat intelligence to adapt to new attack techniques and evolving threats. 

Intrusion Detection System examples

Popular IDS examples in cyber security include:

Snort

• Type: An open-source, network-based intrusion detection system (NIDS) with intrusion prevention system (IPS) capabilities developed by Sourcefire. 
• Key features: Open-source, highly customisable, and widely used in enterprise networks.
• How it works: Combines signature-based and anomaly-based detection to detect and respond to intrusions. It analyses network traffic and compares it against a set of predefined rules or signatures, generating an alert if an intrusion that matches these rules is detected. 
• Strengths: Allows users to create custom rules and modify existing ones, responds to detected threats by generating alerts, logging events, or blocking traffic in real time, and includes a large user community. 
• Use case: Ideal for organisations that need a free but powerful intrusion detection system that also works as an intrusion prevention system (IPS).

Suricata

• Type: A network intrusion detection and prevention system (IDS/IPS) developed by the Open Information Security Foundation. 
• Key features: A multi-threaded engine with deep packet inspection, protocol parsing, file extraction, and logging capabilities. 
• How it works: Uses multi-threaded packet inspection to analyse large amounts of traffic. It supports signature-based detection and protocol parsing for deeper analysis.  
• Strengths: Can handle high-bandwidth environments and has strong support for modern protocols. 
• Use cases: Best for large organisations that need a modern IDS/IPS solution that can handle large network sizes and traffic volumes without losing performance.

OSSEC

• Type: Host-Based Intrusion Detection System (HIDS) maintained by Atomicorp. 
• Key features: Cross-platform support, log analysis, file integrity checking, and rootkit detection. 
• Strengths: Scalable to fit different sized organisations, helps to meet compliance standards (e.g. PCI DSS), and offers community support for updates and improvements.  
• How it works: Uses a central server and agents installed on individual systems to carry out log analysis, file integrity monitoring, rootkit detection, and real-time alerts.
• Use cases: Suitable for a range of differently sized businesses looking for an IDS that supports compliance monitoring.

Why are intrusion detection systems important?

Intrusion Detection Systems play a vital role in ensuring the security and integrity of computer networks and systems. Here’s why IDSs are important:

Early threat detection

IDS continuously monitors network traffic, logs, and data sources to detect intrusions in real-time, enabling prompt incident response and minimizing potential damage. Early detection helps organizations mitigate threats and reduce the chances of successful attacks.

Proactive defense

Intrusion detection systems offer proactive defense against malicious activities and unauthorized access attempts. They identify and block network-based attacks like port scans and DoS attacks, safeguarding digital assets’ availability, confidentiality, and integrity. 

Insider threat detection

IDS can identify suspicious activities initiated by authorized users or insiders with malicious intent. Behavior-based IDS, in particular, can detect anomalies in user behavior, such as unauthorized privilege escalation, data exfiltration, or unauthorized access attempts to sensitive information.

Compliance and regulatory requirements

IDS helps organizations meet compliance regulations by offering continuous monitoring, event logging, and audit trail generation. Demonstrating compliance helps prevent penalties, legal consequences, and reputational harm, ensuring adherence to industry regulations. Pairing your IDS with cybersecurity compliance services helps make sure that your business not only detects threats but also meets compliance requirements. 

Incident response and forensics

An IDS generates alerts for incident response and forensic investigations. Security teams analyze and investigate alerts to mitigate the impact of intrusions. IDS logs and data serve as valuable evidence during forensic investigations, aiding in understanding the breach’s nature, identifying its scope, and facilitating the recovery process.

Enhanced security posture

Integrating an intrusion detection system with other security controls, like firewalls, antivirus software, and SIEM systems, creates a comprehensive security posture. IDS also enhances threat detection capabilities, providing added visibility into network and system activities, resulting in more effective incident response.

Ongoing threat intelligence

Intrusion detection systems benefit from continuous updates and threat intelligence feeds, staying informed about new attack methods and vulnerabilities. This adaptability enables IDS to provide the latest defenses against potential intrusions, keeping organizations protected from evolving threats.

Challenges of intrusion detection systems

While intrusion detection systems are valuable tools in cybersecurity, they also face certain challenges, such as:

• False positives and negatives: IDS can produce false alerts, flagging legitimate activities as potential threats, or miss actual intrusions, demanding careful tuning and continuous improvement of detection rules.
• Evasion techniques: hackers use sophisticated methods to avoid IDS detection, like encryption and low-and-slow attack patterns, requiring IDS to keep up with evolving threats.
• Network complexity: complex networks strain IDS performance, necessitating scalability and optimization for effective monitoring.
• Zero-day exploits: signature-based IDS may miss unknown threats, highlighting the need for anomaly and behavior-based detection methods.
• Resource demands: IDS can be computationally intensive, requiring adequate hardware and resources for optimal performance.
• Response and remediation: Efficient response to IDS alerts requires skilled personnel, well-defined incident response processes, and integration with security workflows.

That’s why many organisations use IDS in combination with continuous security testing, which gives them continuous red teaming to uncover weaknesses before attackers do.

IDS evasion techniques

Cybercriminals actively try to bypass network intrusion detection systems and host-based IDS using:

1. Encryption: by encrypting their communication, attackers can hide the contents of network packets from IDS, making it challenging to detect any malicious payloads or commands.
2. Polymorphic malware: polymorphic malware is designed to continuously change its code or behavior, making it difficult for signature-based IDS to identify the malicious software based on predefined signatures.
3. Fragmentation: cybercriminals may fragment network packets to distribute malicious payloads across multiple packets, helping bypass signature-based IDSs.
4. Traffic manipulation: attackers can use packet-level techniques like source IP address spoofing or fragmenting packets in specific ways to evade detection.
5. Covert channels: cybercriminals transmit data or commands through alternative communication paths that are unmonitored by IDS.
6. Polymorphic shellcode: shellcode employs techniques like code obfuscation, or encryption making it difficult for IDS to recognize and detect malicious code within network traffic.
7. Timing and traffic patterns: by aligning their activities with regular traffic patterns or specific periods of network congestion, cybercriminals evade anomaly-based IDS. 

Things to consider when choosing an IDS

When selecting an IDS system for cyber security, consider:

• Deployment: choose NIDS or HIDS based on your network’s needs, considering where the IDS will be placed within your infrastructure.
• Detection techniques: opt for an IDS with diverse detection methods, combining signature-based, anomaly-based, and behavior-based techniques.
• Customization: ensure the IDS allows customization of detection rules to fit your unique network environment.
• Scalability: verify that the IDS can handle your network’s traffic volume without compromising performance.
• Integration: check compatibility with other security tools for a comprehensive defense strategy.
• Reporting and alerts: look for clear, actionable alerts and reporting capabilities compatible with your incident response processes.
• Vendor support: evaluate the vendor’s update frequency and technical support availability.
• Ease of use: consider user-friendly interfaces for effortless management.
• Cost and budget: weigh the IDS’s cost against its value and effectiveness in meeting your security needs.
• Reputation: research vendor reputation and reviews in the cybersecurity community for insights into system performance and reliability. 

IDS implementation best practices

For effective IDS protection, follow these best practices:

1. Set clear goals for IDS implementation based on risks and compliance needs. 
2. Assess network vulnerabilities to strategically deploy IDS sensors in critical areas. 
3. Create a detailed plan for IDS sensor placement, covering high-risk entry points and sensitive systems. 
4. Choose a suitable IDS solution that considers scalability, compatibility, and integration capabilities. 
5. Customise IDS rules and signatures for your network. 
6. Regularly update IDS software and keep signatures up to date with the latest patches. 
7. Create efficient workflows for handling IDS alerts. 
8. Integrate IDS with firewalls, SIEM, endpoint security, and threat intelligence to enhance security. 
9. Regularly test IDS capabilities with pen testing and vulnerability assessments. 
10. Invest in staff training for effective IDS management and threat response. 
11. Regularly update documentation of IDS configuration, incident response, and customizations.

FAQs

What is the difference between an IDS and an IPS?

An IDS passively monitors network traffic and generates alerts when it detects suspicious or potentially malicious activities. In contrast, an IPS actively monitors and can take immediate action to block or prevent detected threats, offering a more proactive approach to network security.

What is the difference between an IDS and a firewall?

An IDS monitors network traffic for suspicious or malicious activities and generates alerts when potential threats are detected. On the other hand, a firewall acts as a barrier between networks, controlling incoming and outgoing traffic based on predefined security rules, effectively blocking unauthorized access and malicious traffic.

Can IDSs be integrated with other cybersecurity technologies and tools?

Yes, Intrusion Detection Systems (IDS) can be integrated with other cybersecurity technologies and tools to enhance overall security capabilities and improve the effectiveness of threat detection and response.

How does IDS protection help with incident response?

IDSs can facilitate incident response by continuously monitoring network traffic and endpoint activities for signs of suspicious or malicious behavior. When it detects a potential security incident, it alerts security personnel, enabling them to quickly identify and respond to threats, investigate the incident, and take appropriate actions. 

What are some intrusion detection system examples?

Snort, Suricata, OSSEC, and Zeek are well-known IDS examples.

Final thoughts

Intrusion detection systems play a pivotal role in fortifying your organization’s cybersecurity defenses. They provide real-time threat detection, enable proactive defense, detect insider threats, facilitate compliance, aid in incident response, and enhance your security posture.

To harness the full potential of your IDS and protect yourself from the widest range of threats, you must consider your specific needs, such as your security goals and infrastructure.

If you seek expert advice on how to select, deploy, or optimize your intrusion detection system, CovertSwarm is here to assist. We help a variety of industries detect cybersecurity threats and stay secure, including finance, crypto, healthcare, and SaaS. 

Simply contact us and a member of our team will find an empowering solution that keeps you one step ahead of potential intrusions.