Brad Spengler

grsecurity started in 2001 as a set of hardening patches for the Linux kernel and was combined with the PaX Team's memory protections. Much of what later reached mainline — address space randomisation, tighter defences against privilege escalation, stopping the kernel from touching user memory — shipped in grsecurity years earlier.

Relations with the kernel developers were famously frosty. In 2017 Spengler stopped publishing the patches and made them customer-only. When Bruce Perens called the arrangement a likely GPL violation, Spengler sued him for defamation — and lost, including on appeal in 2019.