Network Prefixes in Address Books
You can specify addresses as network prefixes in the prefix/length format. For example, 203.0.113.0/24 is an acceptable address book address because it translates to a network prefix. However, 203.0.113.4/24 is not acceptable for an address book because it exceeds the subnet length of 24 bits. Everything beyond the subnet length must be entered as 0 (zero). In special scenarios, you can enter a hostname because it can use the full 32-bit address length.
https://www.juniper.net/documentation/us/en/software/junos/security-policies/topics/topic-map/security-address-books-sets.html

ICMP flood
Use the ICMP flood IDS option to protect against ICMP flood attacks. An ICMP flood attack typically occurs when ICMP echo requests use all resources in responding, such that valid network traffic can no longer be processed.
The threshold value defines the number of ICMP packets per second (pps) allowed to be send to the same destination address before the device rejects further ICMP packets.
IP spoofing
Use the IP address spoofing IDS option to prevent spoofing attacks. IP spoofing occurs when an invalid source address is inserted in the packet header to make the packet appear to come from a trusted source.
https://www.juniper.net/documentation/us/en/software/junos/denial-of-service/topics/topic-map/security-introduction-to-adp.html