When corporate networks ban unauthorized WiFi routers across 100+ branches, traditional physical detection becomes impractical. The solution lies in network-based detection methods that can:

• Identify unauthorized MAC addresses in switching infrastructure
• Detect rogue DHCP servers
• Analyze wireless protocol frames in wired networks

One effective method involves querying network devices via SNMP to identify wireless interfaces:

import pysnmp.hlapi as snmp

def check_wireless_interfaces(ip, community):
    iterator = snmp.nextCmd(
        snmp.SnmpEngine(),
        snmp.CommunityData(community),
        snmp.UdpTransportTarget((ip, 161)),
        snmp.ContextData(),
        snmp.ObjectType(snmp.ObjectIdentity('IF-MIB', 'ifType'))
    )

    wireless_ifs = []
    for response in iterator:
        errorIndication, errorStatus, errorIndex, varBinds = response
        if errorIndication:
            continue
        for varBind in varBinds:
            if varBind[1].prettyPrint() == 'ieee80211':
                wireless_ifs.append(varBind[0].getOid()[-1])
    
    return wireless_ifs

Rogue APs often run DHCP servers. This script captures DHCP offers and analyzes them:

from scapy.all import *

def dhcp_monitor(pkt):
    if DHCP in pkt and pkt[DHCP].options[0][1] == 2:  # DHCP Offer
        vendor = [opt[1].decode() for opt in pkt[DHCP].options 
                 if opt[0] == 'vendor_class_id']
        if vendor and 'wireless' in vendor[0].lower():
            print(f"Potential rogue AP at {pkt[IP].src} - {vendor[0]}")

sniff(filter="udp and (port 67 or port 68)", prn=dhcp_monitor)

Some APs tunnel wireless frames through Ethernet. This detection script looks for 802.11 frames:

def detect_wireless_frames(pkt):
    if pkt.haslayer(Dot11):
        print(f"Wireless frame detected from {pkt.src}")
        print(f"AP MAC: {pkt.addr3 if pkt.addr3 else 'N/A'}")
        print(f"SSID: {pkt.info.decode() if hasattr(pkt, 'info') else 'N/A'}")

sniff(filter="ether proto 0x88b7", prn=detect_wireless_frames)

Analyzing NetFlow/sFlow data can reveal wireless traffic patterns:

SELECT src_ip, dst_ip, COUNT(*) as packet_count
FROM netflow_data
WHERE (dst_port = 67 OR dst_port = 68)  # DHCP
   OR (protocol = 17 AND port = 1900)   # UPnP
   OR (protocol = 17 AND port = 5353)   # mDNS
GROUP BY src_ip, dst_ip
HAVING COUNT(*) > threshold
ORDER BY packet_count DESC;

For large deployments, consider these open-source tools:

• RogueHunter: SNMP-based detection system
• Kismet: Wireless detection server for remote sensors
• Security Onion: Network monitoring distro with rogue AP detection

When organizations implement strict no-WiFi policies across distributed networks, detecting unauthorized access points becomes critical for security. Traditional physical detection methods aren't feasible for remote offices, requiring automated network-based solutions.

Here are three technical methods to identify rogue WiFi devices:

# Python example using Scapy for passive detection
from scapy.all import *

def packet_handler(pkt):
    if pkt.haslayer(Dot11):
        if pkt.type == 0 and pkt.subtype == 8: # Beacon frame
            print(f"Found WiFi: {pkt.info.decode()} - MAC: {pkt.addr2}")

sniff(iface="eth0", prn=packet_handler, store=0)

More aggressive scanning can reveal hidden access points:

# Bash script using nmap for active scanning
#!/bin/bash
nmap -sn 192.168.1.0/24 | grep -i "router" | awk '{print $5}'

For large networks, consider these professional tools:

• Aruba ClearPass
• Cisco Identity Services Engine
• Ruckus SmartZone

Rogue devices often reveal themselves through network protocols:

# Python DHCP analysis
import pyshark

capture = pyshark.LiveCapture(interface='eth0', display_filter='dhcp')
for packet in capture.sniff_continuously():
    if hasattr(packet.dhcp, 'option_dhcp_message_type'):
        print(f"DHCP request from {packet.eth.src}")

For 100+ branch offices, set up automated alerts using tools like Nagios or Zabbix with custom plugins to detect new MAC addresses appearing on network segments.