Intrusion Prevention System (IPS) and Intrusion Detection System (IDS): What is the Difference?

Lauren Abshire
Editor United States Cybersecurity Magazine

An Intrusion Prevention System – or an IPS – is a network security technology (and control system) that monitors networks and traffic for any vulnerability exploits or malicious activity. IPS will automatically either allow or deny the detected traffic (good or bad) based on its established ruleset. An Intrusion Detection System – or an IDS – essentially does the same with a notable difference: IDS does not take action against potential/detected malicious traffic on its own. (More of a passive technology since it does not outwardly deny traffic.)

While both technologies will read the network packet – a unit of data flowing from point A to point B – and compare it to a database, there are differences between the two. An IPS is a control system while an IDS is a detection/monitoring tool. As mentioned above, an IPS follows a ruleset to determine either a denial or a passage of the monitored traffic, and an IDS monitors and detects the traffic; however, it requires a human to examine any detected threatening results. An IDS will send an alert(s) based on the ruleset/database and an IPS will proactively act based on the ruleset/database. 

For both IPS and IDS to be as effective as possible, the database on threats/cyber-attack patterns must be regularly updated and updated in real-time. As a new threat or attack pattern emerges, it must be added to the database. Both IPS and IDS use a signature-based detection method and where an IDS uses an anomaly-based detection, an IPS uses a statistical anomaly-based detection. However, herein lies another issue: false positives. Since an IDS requires a human to examine results, if there is a false positive, the only person impacted is the designated person for examining said results. On the other hand, if an IPS detects malicious activity within the network packet and shuts down the entirety of the traffic flow… there could be more than one department affected by this. 

IPS and IDS can work cohesively, thus giving an organization the best of both worlds. While IPS monitors the traffic in real-time and provides network security, IDS can be used to develop a thorough understanding of the traffic flow within a network. Both IPS/IDS technologies use machine-learning to examine, understand and learn emerging threats and patterns across the network. Moreover, since both technologies log attack and response, you can use the information to modify your defenses. 

IPS and IDS can also work in conjunction with a firewall. These combined are often referred to as Next-Generation Firewall or Unified Threat Management. It is important to understand the difference between IPS/IDS/Firewall. A firewall will block or allow traffic, IPS will detect and block traffic and IDS will detect and raise the alarm. Most often when deployed, both technologies are placed behind the firewall, wherein the firewall is in front of the network. 

Both Intrusion Prevention System and Intrusion Detection System technologies are an essential part of security and data management. Since they are both configurable, they can be adapted to fit your InfoSec/IT policies. This is great because if you use a single VPN, you can block ‘outside of your designated VPN’ traffic. Additionally, organizations are subjected to compliance regulations and the implementation of IPS/IDS takes care of that compliance checkbox, all the while defending your network and data too. There is too, of course, the automation factor. With automation, resources can be reallocated to other departments and areas. 

Network security is a necessity for organizations; it ‘houses’ all of their ‘belongings’ (data, customer info, and so on). The Intrusion Prevention System and the Intrusion Detection System will not only work for you, but it will also work to keep cybercriminals out of your ‘house’ and prevent them from rooting through your ‘belongings’ and taking whatever they want.


Lauren Abshire

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