[piaskal]

I'd use random data to make it hard to compress. You don't know if there won't be some link layer compression along the way.

[kcbanner]

That doesn't really fix the problem, what if that random data happened to compress well? The solution is to not compress anything while downloading.

[gojomo]

"Random data' [1] will not compress well [2].

[1] high-entropy in any of the usually-available ways

[2] for any compression system actually deployed, as opposed to one contrived to match specifically the 'random' source

[cbr]

A large quantity of random data is incredibly unlikely to compress well.