In a switched environment packets are only sent to devices that they are meant for. Even in this switched environment there are ways to sniff other devices’ packets. As reported in this Sys-Con report, Arp cache poisoning puts the attacker in position to intercept communications between the two computers. Computer. In this “Network Security: Arp Cache Poisoning and Sniffing Packets” article discusses a number of tools used in arp cache poisoning.