Nessus was able to determine if the remote host is alive using one or more of the following ping types :
- An ARP ping, provided the host is on the local subnet and Nessus is running over Ethernet.
- An ICMP ping.
- A TCP ping, in which the plugin sends to the remote host a packet with the flag SYN, and the host will reply with a RST or a SYN/ACK.
- A UDP ping (e.g., DNS, RPC, and NTP).