Block traffic on WAN port

Dear community,

I installed the iftop module to check the router activity on the wan port. I was surprised by the activity on the wan port.
It is constantly communicating 3 ip addresses on wan port:

224.0.0.251:5353 "mDNS" Security risk ?
239.255.255.250:1900 "SSDP" Security risk ?
255.255.255.255:5678 " ? "

Is it safe to block mDNS and SSDP on the wan port via iptables?

If so, please help me how to block these ip addresses either using iptables or shutdown services.

thanks in advance

Openwrt version: stable 21.02.3
PS: I tried newer firmware with nftables firewall. But for me it's easier to use iptables instead of nftables.

https://forum.mikrotik.com/viewtopic.php?t=1792

only you know if you need them.

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