Intrusion Detection Systems | Network Security

Introduction

Intrusion Detection Systems (IDS) are essential components of modern cybersecurity strategies. They are used to detect unauthorized access or abuse of computer systems by monitoring network traffic or system activities.

Types of IDS

There are two main types of IDS:

Network-based IDS (NIDS): Monitors network traffic for suspicious activity.
Host-based IDS (HIDS): Monitors system activities for suspicious behavior on individual devices.

How IDS Works

IDS generally work by using one of the following techniques:

Signature-based Detection: Compares network traffic patterns to a database of known attack patterns or signatures.
Anomaly-based Detection: Monitors network traffic and compares it to an established baseline to detect deviations from the norm.

Example of a Network-based IDS

Let's consider an example of a popular open-source Network-based IDS called Snort.

Snort is capable of performing real-time traffic analysis and packet logging on IP networks. It can detect a variety of attacks and probes, such as buffer overflows, stealth port scans, CGI attacks, SMB probes, and more.

To install Snort on a Unix-based system, you might use the following command:

sudo apt-get install snort

Configuring Snort

Once Snort is installed, you can configure it by editing the /etc/snort/snort.conf file. Here is an example configuration snippet:

# Set the network variables
ipvar HOME_NET 192.168.1.0/24
ipvar EXTERNAL_NET any

# Configure the output plugins
output log_tcpdump: tcpdump.log
output alert_fast: stdout

Running Snort

To run Snort in IDS mode, you can use the following command:

sudo snort -c /etc/snort/snort.conf -i eth0

This command tells Snort to use the configuration file located at /etc/snort/snort.conf and to monitor the network interface eth0.

Example of an Alert

When Snort detects suspicious activity, it generates alerts. Here is an example of an alert generated by Snort:

[**] [1:1000001:0] ICMP Test Alert [**]
[Classification: Misc activity] [Priority: 3]
04/08-14:21:01.123456 192.168.1.100 -> 192.168.1.1
ICMP TTL:64 TOS:0x0 ID:12345 IpLen:20 DgmLen:60
Type:8  Code:0  ID:1   Seq:1  ECHO

Conclusion

Intrusion Detection Systems are a critical part of any cybersecurity infrastructure. They help detect unauthorized access and potential threats by monitoring network traffic and system activities. By understanding how IDS work and how to configure them, you can significantly enhance the security of your network.