To know what Arp spoofers do we have to know what ARP is. ARP (Address Resolution Protocol ) is a protocol used to resolve many different network-layer protocol addresses to hardware addresses (IP address to MAC address).
ARP is used when a router needs to forward a packet from one host to the destination host on the same network. ARP spoofers knows plays with ARP entries cached in the system, it sends fake ARP messages from the spoofer machine to the victim machine, playing with the cached ARP resolved entries in the system and associated the router IP with the spoofer MAC address, so any request to the rounter will be delivered to the attacker machine instead.
To fix that is easy, clear the ARP Cache and everything would be OK. To so; In your windows form drag a timer from the toolbox and write the following code in the timer tick event handler:
System.Diagnostics.Process process = new System.Diagnostics.Process();
System.Diagnostics.ProcessStartInfo info = new System.Diagnostics.ProcessStartInfo();
info.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
info.FileName = "arp.exe";
info.Arguments = "-d";
process.StartInfo = info;
process.Start();
This will clear the spoofed entries and force the system to resolve the MAC address of the router again.
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