XArp: The Complete Guide to Detecting ARP Spoofing
What XArp is
XArp is a network security tool designed to detect and prevent ARP (Address Resolution Protocol) spoofing and poisoning attacks on local networks. It monitors ARP traffic and uses active and passive techniques to identify suspicious mappings between IP addresses and MAC addresses.
Key features
- ARP monitoring: Watches ARP requests and replies to detect abnormal changes in IP–MAC associations.
- Active probing: Sends verification probes to confirm the legitimacy of ARP entries.
- Passive detection: Observes traffic patterns and flags inconsistencies without generating extra network noise.
- Whitelisting: Allows trusted IP–MAC pairs to be whitelisted to reduce false positives.
- Alerts and logging: Generates alerts and keeps logs for forensic analysis.
- Cross-platform clients: Offers versions for Windows and Linux (varies by release).
How it detects ARP spoofing
- Maintains a baseline of known IP–MAC mappings.
- Compares incoming ARP replies against the baseline.
- Uses probing (e.g., ARP requests or ICMP) to validate a device’s claimed MAC for an IP.
- Flags rapid or conflicting MAC changes, duplicate MAC addresses, or gratuitous ARP broadcasts.
Typical deployment and use cases
- Small office/home office networks to protect against local ARP attacks.
- Network administrators monitoring critical subnets.
- Incident response to identify man-in-the-middle (MITM) attempts.
- Educational labs demonstrating ARP vulnerabilities.
Limitations and considerations
- Only protects within a single broadcast domain (LAN); not effective across routed networks.
- Requires local network access to monitor ARP traffic.
- False positives can occur in dynamic DHCP environments unless properly whitelisted.
- Effectiveness depends on keeping the whitelist and detection rules updated.
Basic setup steps (high-level)
- Install XArp on a machine connected to the target LAN.
- Configure network interface in promiscuous mode if supported.
- Populate whitelist with known IP–MAC pairs (e.g., gateways, servers).
- Enable active probing and alerting preferences.
- Monitor logs and respond to flagged incidents (isolate device, verify MAC owner).
Response actions on detection
- Verify the suspicious device physically or via management interfaces.
- Isolate or disconnect the offending host.
- Renew DHCP leases or manually reset correct ARP entries.
- Check for compromised devices or rogue access points.
Alternatives and complements
- Dynamic ARP Inspection (DAI) on managed switches.
- Network segmentation and VLANs.
- Use of static ARP entries for critical hosts.
- IDS/IPS solutions that include ARP protection.
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