IPFW dummy net in FreeBSD was amazing for this. I haven't used it in 20 years. On my home DSL line in the 90s I would get so many hack attempts that it was becoming a nuisance, so I filtered ICMP through a dummy net that both delayed and dropped 10% of the packets. Hack attempts went to zero in 3 days.

Luigi Rizzo is a top notch hacker.

https://github.com/luigirizzo/dummynet