Attacker can simply count the bytes. They can buffer one packet, send ack, and reject it based on bytes transferred. Also it's trivial know when next package st

Attacker can simply count the bytes. They can buffer one packet, send ack, and reject it based on bytes transferred. Also it's trivial know when next package starts. Apt doesn't steam all packages at once, it first send first package with http keep alive then waits until client orders the second package.