A number of different attacks against Linux systems rely on brute-force
techniques using the fork()
system call, so
a new Linux security module (LSM), called “Brute”, has been created to
detect and thwart such attacks.
Repeated fork() calls can be used for various types of
attacks, such as exploiting the Stack
Clash vulnerability or Heartbleed-style flaws.
Version 6 of the Brute patch set was recently
posted
and looks like it might be heading toward the mainline.

Source: LWN.net – [$] Handling brute force attacks in the kernel