Understanding the Differences Between IDS and IPS

Lynn Martelli
Lynn Martelli

Many organizations need help understanding how to be proactive against threats without slowing down productivity. One of the key concepts is implementing a security solution that protects them against cyber attacks without causing false alarms. IDS is a passive technology that monitors network traffic to identify potential threats by comparing patterns and identifiers against a database of known attacks. It then alerts human admins to the danger.


IDS vs IPS, which system is the best? Regardless of the system, IDS and IPS scan their networks for threats. If the tool finds malicious behavior, it alerts a security team to its discovery. The alerts can take different forms, but they’re all designed to make the security team aware of a potential threat, no matter its source. The first IDS systems were host-based and user behaviors to detect attacks on individual machines. As networks grew, the trend shifted toward signature-based detection. Signature-based methods search for bits of information in files and data packets that match known malware patterns. Unfortunately, attackers can and do change their tactics to avoid detection by common signatures. The most comprehensive signature-based tools require massive databases to check against, damaging system performance. Anomaly-based IDS looks for deviations from a model of normal behavior on the network. This model might be a database of common attack patterns or use AI and machine learning to find suspicious activity organically. Anomaly-based systems can be effective, but they’re more limited in scope since they need to look at the actual behavior of each device on the network. Ultimately, they can only alert an admin of unusual behavior; they can’t stop the flow of malicious traffic or block the source.


Whether IDS or IPS, these programs work similarly to spot threats. They monitor the network, alert you when they see something suspicious, and keep logs. They also use anomaly detection and signature-based methods to detect malicious activity. The difference is in the prevention of attacks once they’re spotted. IDS depends on human admins to react to each threat, while IPS uses AI and machine learning to block the danger without intervention. This results in fewer false positives, but it does mean the system may disrupt business processes if it shuts down a server to prevent an attack. When you’re deciding which system to use, consider your goals. If you’re okay with human administrators dealing with threats whenever they occur and can afford disruptions, IDS is your best bet. However, IPS is ideal if you want to automate the process and work on an external network or large website with several servers. Depending on the type of IPS solution you choose, it can monitor your entire network or individual devices within the network. Network-based IPS systems monitor the data and behavior of multiple computers through a network-wide sensor. In contrast, host-based IPS systems only monitor the data and behavior of one computer. The former is more effective as it’s hard for hackers to hide their identities when they continuously work from the same machine.


As the name suggests, a detection system is designed to detect a cyberattack by monitoring network traffic and packets. If it finds something it doesn’t like, it will raise an alert to security administrators. However, an IPS takes the next step and prevents the attack from happening. An IPS can do this through signature, anomaly, or hybrid detection methods. It can also monitor a specific endpoint, such as a host or network traffic. Depending on the network’s security requirements, it can also be deployed as a hardware device or software solution. It is essential to consider the needs of a company before choosing an IDS or IPS solution. For example, if a company has industrial control systems (ICS) that must continue to run, an IPS might shut down traffic to and from those devices. This would negatively impact operations.

Similarly, an IPS might falsely identify legitimate traffic and stop it from protecting the organization from threats. It is important to note that even the best IDS solutions are not immune to all attacks. For example, attackers can avoid IDS detection by coordinating their attacks. This makes it difficult for the IDS to recognize that a scan is occurring. They can also spoof addresses or use proxy servers, making it harder for the IDS to track them down.


IDS and IPS systems monitor network traffic but vary in how comprehensive or targeted their monitoring is. For example, a NIDS system monitors all the devices on a network, whereas a HIDS is installed on individual host computers to detect specific types of attacks and behaviors. Using signature-based or anomaly detection, these tools scan for the activity that matches or resembles known threats. Signature-based detection compares data patterns, packet headers, and source and destination information against a list of known attack signatures and alerts when a match is found. This is an excellent method to identify established, less sophisticated threats, but it doesn’t work well with zero-day attacks that don’t have existing signatures. To overcome this limitation, many security vendors offer IDS and IPS solutions that use machine learning or artificial intelligence to analyze and interpret data to spot malicious behavior that they haven’t seen before. This type of solution is called anomaly detection and can be highly effective at spotting previously unknown threats and behavior. A combination of IDS/IPS is the best choice for organizations needing active protection and monitoring capabilities to protect their business, data, and servers. Once deployed, these programs can continue to watch over the network in real-time and will only stop when turned off or notified that an actual threat has been identified and acted upon.

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