In Wireshark, the filter icmp.type==8 is used to detect ICMP Echo requests, which are commonly used in ping sweep attempts. A ping sweep is a network scanning technique used to determine which of a range of IP addresses map to live hosts. It involves sending ICMP Echo requests (type 8) to multiple hosts and listening for Echo replies (type 0). If an Echo reply is received, it indicates that the host is active. Therefore, the filter icmp.type==8 can be applied to capture these ICMP Echo requests and detect a ping sweep attempt.
References: This information is consistent with network security practices and the use of Wireshark for detecting network attacks, such as ICMP ping sweeps1. The filter icmp.type==8 specifically captures ICMP Echo requests, which are central to the technique of ping sweeping1.