The worktop is heavy enough once you have your tower, monitors etc. On it, that it doesn't need to be screwed or secured down, with enough force it will move, but it's not a worry for me as its pushed up to a wall, if your desk wasn't next to a wall you may need / want some sort of fixing just to be safe.
Only thing fully mounted down are the 4 stand offs on top of the set of draws, I think there screwed in with 4x25mm wood screws.
4 Pcs Adjustable Legs, Stainless Steel Furniture Feet, Table Desk Cabinet Kitchen Adjustable Feet Round with Screws(Adjustable Height 0-10mm)
https://amzn.eu/d/7gtRYcM
These are the stand offs, there's a few different sizes if you want more height from the drawers.