Colorful cybersecurity dashboard

IDS vs IPS vs SIEM: What You Should Know

The earliest days of the Internet were the time of a village with no locks on the doors. The users were academics who loved to give away information and trusted each other. There was the occasional prank, but people could live with it.

Then the public got on the Net, and the story became quite different. Viruses and worms appeared. Systems needed protection against hostile access. Necessity led to the development of intrusion detection systems (IDS) and intrusion prevention systems (IPS). They alerted administrators to hostile activity and stopped it from doing harm.

The early attacks were simple ones, taking advantage of glaring software weaknesses. The harm was usually easy to fix, even if it cost time. Firewalls did a pretty good job just by blocking hostile addresses and limiting port access. But as billion-dollar companies have moved onto the Web, the intrusions have evolved into high-stakes crime. People with professional skills put all their effort into devising ways to break into secure systems. Malware as a service has become a reality.

The creators of security measures have kept pace. One of the most valuable developments, going beyond IDS and IPS, is SIEM, Security Information and Event Management. Rather than just looking for specific indicators, it constructs a comprehensive picture of a network’s activity. It looks everywhere for suspicious behavior patterns. It finds threats that less sophisticated security systems miss.

The path to SIEM was a long one, with constant improvements. Threat protection will continue to evolve to meet new tactics.

What is an Intrusion Detection System and an Intrusion Prevention System?

IDS and IPS systems are two parts of network infrastructure that detect and prevent intrusions by hackers. Both systems compare network traffic and packets against a database of cyber threats. The systems then flag offending packets.

The primary difference between the two is that one monitors while the other controls. IDS systems don’t actually change the packets. They just scan the packets and check them against a database of known threats. IPS systems, however, prevent the delivery of the packet into the network.

IDS vs IPS: Definitions

  • Intrusion Detection System (IDS): An IDS system monitors and analyzes network traffic for packets and other signs of network invasion. The system then flags known threats and hacking methods. IDS systems detect port scanners, malware, and other violations of system security policies.
  • Intrusion Prevention System (IPS): An IPS system resides in the same area as a firewall, between the internal network and the outside internet. If the IDS system flags something as a threat, the IPS system denies the malicious traffic. If the traffic represents a known threat in the databases, the IPS will shut the threat out and not deliver any malicious packets.

Some manufacturers of IDS and IPS technologies merge the two into one solution. This solution is known as Unified Threat Management (UTM).

Back to top

The history of IDS, IPS, and SIEM

The first well-documented IDS came from Stanford Research Institute in 1983. It applied statistical methods to audit trails to identify anomalous activity. The Intrusion Detection Expert System (IDES) soon followed, using a rule-based approach to spot suspicious behavior. NIDES (Next-Generation Intrusion Detection Expert System) followed, looking for suspicious patterns of behavior. Its “resolver” component screened out false positives. These early systems used techniques that would later be adopted on a much larger scale.

For a while, the trend shifted toward signature-based detection. Malware can often be recognized by specific bit patterns, called signatures, in affected files or packets. Early behavior-based IDS had many false positives, while a bit pattern is unlikely to be a chance match. However, signature matching had its own problems, as the number of patterns to match grew into the thousands. It started to drag down system performance. Besides, it couldn’t catch previously unidentified threats.

The earliest intrusion detection systems were deployed on their host machines. As networks grew in size and complexity, people recognized the need to protect the whole network, not just individual machines. Networks deployed both host-based and network-based IDS for more complete coverage.

Back to top

IDS vs IPS: How They Work and Why They are Important to Cybersecurity

IDS and IPS systems are important factors in any network. They work in tandem to keep bad actors out of your personal or corporate networks.

IDS systems only look for suspicious network traffic and compare it against a database of known threats. If suspicious behaviors are similar to known threats on the database, the Intrusion Detection System flags the traffic. IDS systems do not operate on their own. They require a human or application to monitor scan results and then take action.

IPS systems work proactively to keep threats out of the system. The Intrusion Prevention System accepts and rejects network packets based on a specified rule set. The process is simple. If packets are suspicious and go against a specified ruleset, the IPS rejects them. This ensures the traffic doesn’t reach the network. IPS systems also require a database that is consistently updated with new threat profiles.

While the two systems seem similar in name and operation, they have a few differences. 

Back to top

What is the Difference Between an IDS and IPS System?

While both systems analyze threats, it’s the steps taken after threat identification that sets them apart. These differences include:

  • An IDS system requires human interaction. IDS systems scan networks for threats, but require human interaction to read the scan results and determine a plan of action to resolve any identified threats. This work could require a full time position if the network generates a lot of traffic. IDS systems make an excellent forensics tool for security researchers investigating a network after a security incident.
  • An IPS system works on autopilot. An IPS system catches and drops any threatening traffic before it causes damage. IPS systems work automatically to scan network traffic and prevent known threats from entering the network.

IDS vs IPSAlthough both systems provide security, neither have a “set it and forget it” approach. Users should remember these systems scan against known security threats. As such, these tools need regular updates. If the databases are up to date, the system performs more effectively.

Remember, a security tool can’t check for threats it doesn’t know exist! 

Back to top

What Security Problems Do Both Systems Solve?

Network security is one of the most important things for corporations to keep in mind. When a business protects sensitive customer information like names, addresses, and credit card numbers, network security is even more important. Staying ahead of cyber criminals is another way IDS and IPS systems help organizations and individuals protect their security.

These systems detect and prevent hackers from getting into the network. 

Early detection and prevention is essential for system administrators and network managers. Staying ahead of hackers is critical when protecting your network. Preventing entry into your network is easier than cleaning up after the damage is done.

Back to top

IDS and IPS systems boost your cybersecurity strategy

  • Automation. In network security, automation is a huge boost. IDS and IPS systems primarily work on autopilot, scanning, logging and preventing malicious intrusions.
  • Hard-coded security policy enforcement. IDS and IPS systems are configurable and allow the systems to enforce security policies at the network level. Even if only one approved VPN is used by your company, you can block any other forms of traffic.
  • Security compliance. Compliance is important for network administrators and security professionals. If a security incident happens, you will need data to show adherence to security protocol. Technologies like IDS and IPS can provide data needed for any potential security investigations.

Not only do these systems detect and prevent intrusions, but they also give you peace of mind. Not having to sit in front of a computer to monitor traffic all day is a great feeling for security professionals.

Back to top


Network security has been heading in a more holistic direction, getting information from multiple sources. The technology for correlating security information goes by the name SIEM, for Security Information and Event Management. (Surprisingly, it’s pronounced “sim,” not “seem.”)

An IPS focuses on incoming and outgoing Internet traffic. SIEM gathers information from many sources, correlating all the available information available. This lets it not only detect active threats but find hidden weaknesses and threats. Its inputs include system and application logs as well as live IDS and IPS data.

SIEM has been around since the end of the twentieth century, making it as old as IPS. However, the earliest systems by that name weren’t the comprehensive approach to security which we expect today. The early systems faced scalability limits, and their correlation of information to produce useful notifications was very limited.

The Complete Guide to Cybersecurity Logging and Monitoring

It took several technical advances for SIEM to fulfill its promise. A major one was the adoption of large NoSQL databases for the efficient handling of huge amounts of log data. The addition of sophisticated analytics greatly increased the usefulness of its reports, letting analysts haul in usable information from a sea of data. Cloud-based SIEM offered almost unlimited scalability. Dashboards provided a single focus for all the information, allowing faster identification and resolution of problems.IDS vs IPS vs SIEMSIEM is not a replacement for IDS and IPS. Rather, it’s a more comprehensive approach that makes use of them. IDS and IPS still stand at the front door to screen visitors and keep trespassers out. SIEM uses the information from IDS, IPS, logs, and firewalls to construct a full picture of network security and take measures beyond the screening of hostile traffic. Logs provide the “information” part of the acronym; the others provide the “event” part.

Nor is SIEM a replacement for human expertise. It provides information for administrators and analysts to use. In straightforward cases, it can take automated action, but many apparent security incidents are judgment calls or don’t have a quick and obvious solution. People with the skills to assess a report’s seriousness and urgency have to make the decision in these cases.

The increasing complexity of networks and threats makes it necessary to bring together as much security-related information as possible. Not every network has the size and security needs to justify SIEM, but the rate of adoption is growing.

Back to top

How a SIEM system works

Setting up a SIEM system is more complicated than installing an IDS or IPS. Companies that use it typically have large networks. It needs access to many information sources. It can be deployed either on-premises or as a cloud service; modern systems are usually cloud-based for greater scalability.



Before touching the software, IT management should establish a list of objectives. What information needs the highest priority for protection? What policies should the system follow? Who should have access to the generated information? In brief, what results are expected?

The planning stage includes building a complete network inventory. Knowing all the places that have Internet access or hold important information is a requirement, or the system will have blind spots.


The planning stage leads to concrete configuration decisions. What information sources should SIEM have access to? How should alert thresholds be set? How should people be notified? What information should the dashboard present?

What needs reporting is a matter of policy and judgment. Compliance with privacy and security standards, such as HIPAA and GDPR, is very important when they apply. Rules can be set up to catch laxness in protecting information. Guarding against situations that can’t happen only overloads the system or triggers false alarms; for instance, attacks based on Drupal-specific vulnerabilities are of no concern if you never use Drupal.

A tricky question is how much should remediation be automated. An automated response can deal with a threat faster than people can. It reduces the damage and lets the staff focus on the more difficult issues. However, it might have unwanted effects that a nuanced human response could avoid. Disabling an account or quarantining a system in response to a false positive annoys the people affected and hurts productivity. Relying too much on automation could make IT staff complacent.

Setting up a SIEM environment involves many software components. Information sources need to be connected. Developers will have to create data conversion scripts. Access to SMS, email, or other channels for alerts needs setting up. If SIEM is used together with an IPS, they need to work together without conflict. When two systems compete to fix the same threat, they could have unexpected effects.

The inputs to SIEM come in different formats. It will need input agents and adapters, including custom scripts in some cases. Giving it access to a rich set of information without creating risks is a security challenge in itself. SIEM is not just another software installation, but a task in which security experts must take an active role.

SIEM should be integrated with a threat intelligence source. That way, it will receive regularly updated data on current threats and adapt its algorithms to catch them. New threats constantly appear, and old ones take new forms. Without regular threat intelligence updates, a network is vulnerable to the latest hostile innovations.

Working with a SIEM system

People need to be assigned roles. The best results come from having a security operations center (SOC) with analysts and engineers who have strong data security skills. The SOC can be outsourced, but it needs contacts in the IT department who can make informed decisions. Roles of responsibility need to be established so that everyone will know exactly what is expected.

The human element is essential to success. IDS, IPS, and SIEM need constant attention. The administrators who manage them will have to adjust the settings as they gain experience and the situation changes. New systems need to be integrated with the set of information sources. Alert thresholds may need raising or lowering.

The status reports that the system issues are as important as the alerts. They identify areas that need improvement and risks that should be corrected.

10 Ways to Maximize Your SIEM Investment

The relevance of SIEM reports depends on the quality of the data it receives. Logs will need adjustment over time to provide more relevant information and less noise. The configuration needs regular attention to produce good results.

The network will change over time. New machines and services need to be integrated into SIEM’s set of information sources. Log output may change with new application releases, requiring adjustments to their connections.

Many businesses find that using a managed security services provider (MSSP) is the best way to manage a SIEM system. It ensures that updates will happen regularly and alerts will get the attention they need. It can maintain a SOC more cost-effectively than most businesses can. However, the IT department needs to make sure that the MSSP stays abreast of changes in the network and that its practices match company policies.

Back to top

For advanced protection

Reacting to threats isn’t enough. A secure network needs to stay ahead of them. It has to keep its protection strong and adjust it as the environment changes. SIEM offers more than just incident detection and prevention. It detects weaknesses and bad practices that could lead to trouble, as well as hostile activity before it becomes a full-scale attack.

Intrusion starts out as subtle probing. Hostile actors look for signs of vulnerability such as outdated software, lack of limits on login attempts, and open ports. They analyze the results before deciding where to focus their efforts.

Persistent malware tries to be subtle. It limits the rate that it infiltrates information so that it won’t trigger alarms. Sometimes its only effect is to steal processor cycles for tasks such as mining cryptocurrency. It may set systems up in a botnet that does nothing until the day it’s called up for a major DDoS attack. Discovering anomalies like this takes an in-depth analysis of network behavior, not just the detection of overtly hostile traffic.

Careless employee practices increase risks. Overuse of privileged accounts, visits to unsafe websites, and remaining logged in 24 hours a day are risky behaviors and may violate company policy. Setting up SIEM to detect these habits lets administrators know about them. They can tighten the technical restrictions or issue warnings.

SIEM tools can detect unusual patterns of account usage. If there is activity from a distant location outside of working hours, it might just be on-site work for a customer in another time zone. It could also mean the account has been compromised or an employee is using it for questionable purposes. Administrators should take a moment to find out which it is.

Back to top

To adopt or not?

Every network is unique. It has a certain size, level of security needs, and budget. A small network that doesn’t manage confidential data has different needs from an enterprise-class network with sensitive personal information. Some organizations find that the combination of a firewall, an IDS, anti-malware software, and awareness training meets their needs.

However, underestimating security requirements can be a costly mistake. If there’s any doubt, the place to start is a comprehensive security assessment, determining the level of risk and the potential consequences of a serious incident. If the risk is significant and the network is complex enough, management should look into SIEM. The question to consider is how well it will improve security compared with other tools and how the cost compares. The study needs to look at the time to set it up, the personnel requirements, and both initial and ongoing costs.

BitLyft offers managed SIEM services as part of its AIR platform. If you’re looking into how SIEM can improve your organization’s security posture, talk with one of our experts. We will present a range of alternatives based on your requirements and budget. In today’s world, strong security is a requirement for every business.

Jason Miller

Jason Miller, Founder and CEO of BitLyft Cybersecurity, has dedicated his 20-year IT career, including co-founding SaaS pioneer Reviora, to removing cybersecurity barriers for mid-sized enterprises. Establishing BitLyft in 2016, Jason set out to unburden security teams with innovative, approachable, and affordable solutions, a vision which has made BitLyft a respected managed detection and response provider. Outside his cybersecurity pursuits, Jason is an avid tree farmer and outdoor enthusiast, planting nearly 300 trees on his ten-acre plot and finding joy in hiking, hunting, and driving his white Tesla Model 3. His diverse passions mirror the balanced blend of expertise, dedication, and joy he brings to BitLyft.

More Reading

cyber graphic of cloud with a padlock inside of it
On-Prem SIEM vs. Cloud: What’s the Difference?
When it comes to cybersecurity, having a cloud-based Security Information Event Management (SIEM) or on-prem SIEM solution is a game changer for protecting your digital assets. However, with two...
cyber code and graphics
SIEM vs MSSP: What's the Difference?
Cybersecurity incidents are a constant threat to modern organizations. Security solutions must be robustly addressed in order to prevent data breaches, hacks, and numerous other security-related...
row in a server farm with server cabinets on both sides of the isle
Managed SIEM vs. SIEM On-Prem: Pros & Cons
Security Information and Event Management, also known as SIEM technology, is a crucial part of any organization’s cybersecurity strategy. But should you install your SIEM tools on-prem? Or should you...