Screens on an SRX Series device protect against which two types of threats?

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