What Is a Network IDS and Why Do You Need It?

There are a variety of tools available to detect attacks and exploits and take steps to block or stop cyber attacks. Things like firewalls to prevent unauthorized traffic from entering the network, spam filters to reject unwanted email messages, and antimalware tools to protect endpoints from malware are universal across just about every organization, regardless of size or industry. Another valuable security tool that is almost as ubiquitous is a network IDS—or intrusion detection system. Let’s take a closer look at what a network IDS does and how it can help you protect your network and secure your data.

What Is an IDS?

IDS is an acronym for “Intrusion Detection System.” One definition for IDS explains, “An IDS (Intrusion Detection System) is a device or application used to inspect all network traffic and alert the user or administrator when there has been unauthorized attempts or access.”

Unlike a firewall, which sits at the perimeter and acts as a gatekeeper to monitor network traffic and determine if it should be allowed into the network or endpoint at all, an IDS focuses on the traffic that is on the internal network to identify any suspicious or malicious activity. This allows an IDS to detect attacks that manage to slip past the firewall, as well as attacks that originate from within the network.

Most IDS solutions use a combination of signature-based detection, which compares traffic against a database of known attacks or attack techniques, and anomaly-based detection, which simply looks for suspicious activity or behavior that is strange or varies significantly from the established norm to detect threats.

Why You Need Network IDS

No firewall is foolproof, and no network is impenetrable. Attackers continuously develop new exploits and attack techniques designed to circumvent your defenses. Many attacks leverage other malware or social engineering to obtain user credentials that grant them access to your network and data. A network intrusion detection system (NIDS) is crucial for network security because it enables you to detect and respond to malicious traffic.

The primary purpose of an intrusion detection system is to ensure IT personnel is notified when an attack or network intrusion might be taking place. A network intrusion detection system (NIDS) monitors both inbound and outbound traffic on the network, as well as data traversing between systems within the network. The network IDS monitors network traffic and triggers alerts when suspicious activity or known threats are detected, so IT personnel can examine more closely and take the appropriate steps to block or stop an attack.

Taking Action on Network IDS Alerts

Network IDS is important for comprehensive security, but there are a few things you must keep in mind to use NIDS effectively. When monitoring and analyzing network traffic for suspicious or potentially malicious activity, there may be false positives and false negatives, and it’s critical to have IT personnel with the knowledge and skills to make decisions and take the necessary action based on the network IDS alerts.

False Positives

Signature-based threat detection is generally accurate, but when it comes to anomaly-based detection and identifying potential suspicious or malicious activity you will likely encounter false positives. A false positive is when the network IDS flags normal activities or legitimate traffic as suspicious or malicious. The intrusion detection system needs to have a solid baseline of what normal traffic looks like and be properly tuned to ignore legitimate or allowed traffic.

False Negatives

On the other side of the spectrum from false positives, you also face a risk that suspicious or malicious activity will not be detected 100 percent of the time. This is particularly an issue with zero day or emerging threats that rely on new exploits and attack techniques that the IDS is unfamiliar with.

Security Experts

With a network IDS, the biggest challenge—aside from false negatives and false positives—can be the sheer volume of alerts. One of the most important elements of using a network intrusion detection system effectively is ensuring you have IT security personnel with the knowledge and skills to necessary weed out false alarms and identify suspicious or malicious traffic the network IDS might have missed.

Attacks don’t have work hours—they occur around the clock every day of the year. You should have a security operations center (SOC) with security experts who can monitor alerts and analyze log data to identify and prioritize potential attacks and take the appropriate action to block the traffic or thwart the attack.

About the Author

Tony Bradley - Senior Manager of Content Marketing for Alert Logic

Tony Bradley

Tony Bradley is Senior Manager of Content Marketing for Alert Logic. Tony worked in the trenches as a network administrator and security consultant before shifting to the marketing and writing side of things. He is an 11-time Microsoft MVP in security and cloud and has been a CISSP-ISSAP since 2002. Tony has authored or co-authored a dozen books on IT and IT security topics, and is a prolific contributor to online media sites such as Forbes and DevOps.com. He has established a reputation for effective content marketing, and building and engaging a community and social media audience.

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