
PT_DENY_ATTACH is a non-standard ptrace() request type that prevents a debugger from attaching to the calling process. Adam Leventhal
recently discovered that Leopard extends PT_DENY_ATTACH to prevent introspection into processes using dtrace.
This article will cover disabling PT_DENY_ATTACH for all processes on Mac OS X 10.5. Over the previous few years, I've provided similar hacks for both Mac OS X 10.4, and 10.3.