How to Detect Network Intrusions Using Python

Network security is a critical aspect of cybersecurity. Detecting intrusions in a network helps prevent unauthorized access, data breaches, and cyber attacks. In this guide, we will explore how to use Python and the Scapy library to detect suspicious network activity.

What is Network Intrusion Detection?

Network Intrusion Detection Systems (NIDS) monitor network traffic for malicious activity. This can include detecting port scans, unusual packet patterns, or unauthorized connections.

Installing Required Libraries

Before starting, install Scapy:

    pip install scapy
    

Capturing Network Packets

We can use Scapy to capture packets and analyze them for suspicious activity.

    from scapy.all import sniff

    def packet_callback(packet):
        print(packet.summary())

    sniff(prn=packet_callback, count=10)
    

Detecting Port Scanning

Port scanning is a common technique used by attackers to find open ports. We can detect it by monitoring for multiple connection attempts from a single IP.

    from scapy.all import sniff
    from collections import defaultdict

    scan_attempts = defaultdict(int)

    def detect_port_scan(packet):
        if packet.haslayer('IP') and packet.haslayer('TCP'):
            ip_src = packet['IP'].src
            scan_attempts[ip_src] += 1
            if scan_attempts[ip_src] > 10:
                print(f"Possible port scan detected from {ip_src}")

    sniff(prn=detect_port_scan, store=0)
    

Detecting Suspicious Payloads

We can also inspect packet contents for known attack signatures.

    def detect_malicious_payload(packet):
        if packet.haslayer('Raw'):
            payload = packet['Raw'].load.decode(errors='ignore')
            if "malicious" in payload:
                print(f"Suspicious payload detected: {payload}")
    
    sniff(prn=detect_malicious_payload, store=0)
    

Conclusion

By using Python and Scapy, we can detect potential network intrusions, port scans, and malicious payloads. Implementing such monitoring techniques is crucial for network security and cybersecurity defenses.