Arpspoof

Arpspoof is a network security tool designed to perform ARP spoofing or poisoning on a local area network. It is part of the dsniff suite developed by Dug Song. The program automates the sending of forged ARP replies to misrepresent the attacker’s MAC address as the MAC address for another host, typically the gateway, on the target’s IP address. Because ARP lacks authentication, such poisoning can redirect a victim’s network traffic through the attacker’s machine.

In operation, arpspoof can target a single host or multiple hosts to establish a man-in-the-middle position on the LAN. By convincing a target that the gateway IP is associated with the attacker’s MAC, and, if used in both directions, by also poisoning the gateway’s ARP cache, the attacker can intercept, monitor, and potentially modify the traffic between the two endpoints. The technique is most effective on untrusted or poorly secured local networks and is less reliable on modern switches with features that constrain ARP broadcasts.

Uses and limitations: arpspoof is commonly employed in security assessments and educational demonstrations with proper authorization. It can enable traffic capture with packet analysis tools, and may facilitate credential harvesting or data modification when combined with other tools. On protected or well-configured networks, ARP poisoning is harder to sustain, because of caching behavior and defensive measures.

Mitigation and defense: static ARP entries, dynamic ARP inspection, and DHCP snooping reduce ARP spoofing risks; network segmentation, switch port security, and the use of VPNs or encrypted channels also help mitigate the threat. Ethical and legal considerations require obtaining explicit permission before using arpspoof on any network.