Intrusion Detection Systems (IDS): What is an IDS, and how does it protect Businesses?

Intrusion Detection Systems IDS
Image Credit: juststock/Getty Images

What are Intrusion Detection Systems (IDS)? With the recent remote working trend, the threat landscape has expanded overnight. Analyzing traffic flows and detecting vulnerabilities in such a complex IT environment is challenging and critical.

In such a scenario, intrusion detection systems are a trump card in the hands of enterprises looking to build a robust security system around their network.

What are Intrusion Detection Systems?

Intrusion detection systems are devices or software programs that monitor network traffic for malicious activity or policy breaching and report them once discovered.

Any suspicious activity or policy violation is typically reported to the system administrator or collected in a centralized location using a SIEM network.

As software, IDS can be installed on any system or can be used as a network security application. Cloud deployments can shield data and networks through cloud-based intrusion detection systems.

Intrusion Detection Systems (IDS) vs Intrusion Prevention Systems (IPS)

Intrusion detection involves the monitoring of network events and analyzing them for indications of possible incidents, security policy violations, or imminent threats. An intrusion detection system is primarily an alerting system that notifies a company whenever suspicious or malicious behavior is identified.

Intrusion prevention is the process of doing intrusion detection and subsequently halting occurrences that have been discovered. A network intrusion prevention system takes this detection further by disabling the network access that can be gained and limiting any further network movement.

Intrusion detection systems (IDS) and intrusion prevention systems (IPS) solutions integrate into your network to identify and prevent potential occurrences.

Intrusion Detection Systems (IDS) vs Firewalls

An IDS and a firewall look after the network security but are significantly different entities. IDS is a software or hardware device put on the network (NIDS) or host (HIDS) to detect and report network intrusion attempts.

A firewall keeps an eye out for intrusions externally so that it can prevent them from happening. Firewalls prevent intrusion by restricting access between networks.

A firewall can also be a hardware device or software that operates in a networked environment to prevent unwanted access while allowing permitted connections. A firewall is a device or software that sits between a local network and the Internet and filters potentially hazardous information.

How does an Intrusion Detection System work in a network?

Intrusion detection systems are strategically located at endpoints or points inside the network. From there, they monitor the internal and external from all devices on the network. It analyzes the passing traffic by matching it on the subnet to the library of previously known attacks.

Once abnormal activity or deviations are reported, they are propped up on the stack for analysis at the protocol and applications layer.

Benefits of Intrusion Detection Systems

The starting point of IDS is its ability to detect security incidents. It can analyze the frequency and types of attacks organizations can use to change their security systems or implement better controls.

An intrusion detection system can also help organizations detect bugs or issues in their device configurations. Companies can use these metrics to assess their future security risks.

With greater visibility across their entire network, intrusion detection systems make it easier for enterprises to achieve regulatory compliance. Moreover, businesses can use the IDS seal in their documents to show that they meet security regulations requirements.

Intrusion detection systems can be used to make overall security responses more effective. Since it can detect network hosts, it can also be used to identify the OS of services used or analyze data within network packets. Utilizing an IDS to gather this information is more efficient than doing it manually.

Along with increasing security, intrusion detection systems can help companies organize their critical network data. Every organization generates tons of network data through daily operations. Intrusion detection systems can help distinguish between necessary and less essential activities.

By enabling you to direct your attention towards critical data, intrusion detection systems can free resources from sifting through tons of data on the system to find out crucial information. This reduces the chances of human error, decreases manual labor, and saves time.

Types of Intrusion Detection Systems

From tiered monitoring systems to antivirus software, a wide array of IDS monitors an entire network’s traffic.

Network Intrusion Detection System (NIDS)

Network-based IDS solutions monitor incoming network traffic on an entire protected network. It examines all the flowing traffic and matches the traffic to the collection of known cyber attacks, using packet metadata and contents.

Once the NIDS detects an anomaly or a breach, a notification is sent to the system administrator. A typical example of NIDS would be its installation on the subnet where firewalls are located to prevent potential attackers from breaching the firewall.

Due to its broad viewpoint, NIDS offers better context and also comes with the ability to identify widespread threats. However, these systems do not have much visibility into internal endpoints.

Host Intrusion Detection System (HIDS)

HIDS operates on independent devices or hosts in the system. It will monitor incoming and outgoing traffic only from that particular device and will alert the administrator if any suspicious activity or malicious traffic is identified.

HIDS has the edge over NIDS in that it can identify anomaly-filled network packets or malicious traffic that originate inside the network, which NIDS failed to detect. HIDS may also detect malicious activity that originated from the host.

In these cases, the host can be infected with malware trying to spread to the network.

Protocol-Based Intrusion Detection System (PIDS)

PIDS is located at the front end of a server. From there, it efficiently monitors and interprets the arrangement between the server and a user. It is responsible for securing the web server by consistently monitoring HTTPS protocol streams.

Application Protocol-Based Intrusion Detection System (APIDS)

APIDS is located within a group of servers. It works by interpreting the communication on application-specific protocols.

Hybrid Intrusion Detection System

As the name suggests, a hybrid system is created by a hybrid of two or more approaches of the IDS.

System data is merged with server information to gain complete visibility of the network system. Hybrid intrusion detection systems work more effectively than other detection systems.

Detection Methods

Signature-Based Method

This IDS method detects cyber-attacks based on specific patterns. For example, the number of 0s or data units detected in the server traffic.

It also looks for already known malicious instructions used by the malware. IDS identifies these patterns as signatures.

Signature-based IDS effectively detects attacks based on patterns in the system. However, since their unknown patterns, it fails to detect new malware attacks.

Anomaly-Based Method

As new malware is developed rapidly, an anomaly-based method was newly created to identify and adapt to this unknown malware.

Anomaly-based detection utilizes machine learning technology to create a trustable activity model. The model is developed based on what is considered normal regarding the security policy, protocols, bandwidth, ports, and other devices.

Any incoming activity is compared with this model and is declared suspicious if it does not match.

Since machine learning models can be trained according to applications, machine learning-based detection has a better-generalized property than signature-based detection systems.

While anomaly-based detection can quickly identify previously unknown attacks, the approach can fall prey to false positives. Previously unidentified genuine activity can be mistakenly classified as malicious in such cases.

Evasion Techniques

Knowing cybercriminals’ techniques to breach system security can help IT departments fine-tune their IDS systems into not missing any actionable threats.

  • Fragmentation: By forwarding fragmented packets, attackers can dodge through the detection system’s ability to identify the pattern of the attack. This way, attackers can stay under the radar and carry out attacks.
  • Address Spoofing / Proxying: Attackers use poorly protected or improperly configured proxy servers to conceal the source of the attack.
  • Pattern Change Evasions: Since IDS relies on matching patterns, slight tweaks to the attack architecture can easily avoid detection.
  • Low-bandwidth coordinated attacks: In this evasion technique, attackers coordinate scans amongst themselves or even allocate different hosts and ports to other attackers. By doing so, IDSes can struggle to correlate the captured packets and figure out that a network scan is ongoing.
  • Source Port Manipulation: Using source port manipulation, attackers manipulate the actual numbers of the ports with standard port numbers, thereby bypassing firewall and IDS rules. In the simple sense, it entails masking the ports blocked by using the ports authorized by the IDS or firewall configuration rules.

Drawbacks of IDS

IDS operates on a listen-only approach wherein the system can monitor traffic and report its analysis to the administrator. Still, it cannot take any action against the detected exploit.

Attackers quickly take advantage of vulnerabilities once they are inside the network. This renders IDS an inadequate system for prevention.

As mentioned earlier, an IDS can be prey to false alarms. To avoid this, companies must fine-tune their IDS solutions during the first installation. Fine-tuning includes configuring their IDS to understand how regular traffic on their network appears in contrast to potentially suspicious activity.

However, false positives do not severely affect the existing network. It only leads to configuration improvements. A more severe blunder is a false negative, wherein IDS misses a threat, mistaking it for genuine traffic.

With false negatives, security teams don’t realize an attack is taking place. They discover it only after the attack has caused some damage to the network.

False negatives are a growing concern to IDSes, especially SIDSes since malware is becoming more sophisticated. SIDSes find it challenging to detect an intrusion because evolved malware may not show previously detected patterns. As a result, it’s the need of the hour for IDSes to understand new behavior and their evasion techniques.


The way cyber attacks are being carried out is getting increasingly sophisticated. Malware can morph into signature defeating variants and communicate via encryption or side channels. Malware now also can blend into regular network traffic to flow unnoticed.

A comprehensive and adaptable intrusion detection system is not a panacea. It is just one layer of a good defense strategy. It will never be an adequate barrier on its own. Signature-based IDS are easy to beat, and anomaly-based detection can suffer from high rates of false positives.

Despite the limitations, IDS is a necessary aspect of security. It can protect your cloud-based or On-Prem IT networks from cyber threats and malicious traffic.

You might also like