How to disable custom 404.php

Hello
My site is often attacked by bots who try to access pages that never existed. Each time they try accessing a non existent page they are being redirected to 404.php. The effect is similar to that of a DDOS attack and my cpu load spikes almost freezing the vps. I want to completely disable the 404.php page and replace it with something less resource intensive. A static page would be good but I think stopping it htacess level is probably better. I added this line to htacess ErrorDocument 404 “<H1>page not found</H1>” but the custom 404 page is still loading. Can you give some advice on how to do it please?
Kind regards,
Tunc
kanalfinans.com

Well, WordPress does the redirect to the 404 page, so you actually need to redirect the 404 to a page not text. You could simply modify the existing 404 template to be a single html page with a message, which is best solution.

Just edit the existing theme 404 template.