Products
Platform
General
Public groups
we have set of Ransomware public IPs that need to block in layer 3 policy
You can block specific IP's in the MX Layer 3 firewall rules under Security & SD-WAN -> Firewall.I'd also suggest blocking some of the security related categories under content filtering.
like i have trying to block specific public ip it shows only ipv6 can block
Use the outbound rules.
Inbound ipv4 sessions are blocked by default
https://documentation.meraki.com/MX/Firewall_and_Traffic_Shaping/MX_Firewall_Settings#Outbound_rules
As a minimum use opendns as your dns servers. This will already help a lot.