It was lightening-fast but too primitive &amp; had weaknesses. Something like EROS (capability-secure kernel) or INTEGRITY-178B (separation kernel) were more ideal. Back when I was implementing, I did work with L4 (esp OKL4) based on the Nizza Security Architecture:<p><a href="http:&#x2F;&#x2F;genode-labs.com&#x2F;publications&#x2F;nizza-2005.pdf" rel="nofollow">http:&#x2F;&#x2F;genode-labs.com&#x2F;publications&#x2F;nizza-2005.pdf</a><p>Case study for a secure, IPsec VPN with Nizza below:<p><a href="http:&#x2F;&#x2F;citeseerx.ist.psu.edu&#x2F;viewdoc&#x2F;download;jsessionid=B12EF1739E0D9515BC0B892BC05833BB?doi=10.1.1.65.6309&amp;rep=rep1&amp;type=pdf" rel="nofollow">http:&#x2F;&#x2F;citeseerx.ist.psu.edu&#x2F;viewdoc&#x2F;download;jsessionid=B12...</a><p>Applied to secure filesystems<p><a href="https:&#x2F;&#x2F;www.usenix.org&#x2F;legacy&#x2F;event&#x2F;atc11&#x2F;tech&#x2F;slides&#x2F;weinhold.pdf" rel="nofollow">https:&#x2F;&#x2F;www.usenix.org&#x2F;legacy&#x2F;event&#x2F;atc11&#x2F;tech&#x2F;slides&#x2F;weinho...</a><p>You can do a lot with that model whether you use a recent L4 kernel or some other microkernel. If you&#x27;re into that stuff, I&#x27;d say check out the GenodeOS project at genode.org. Unlike most, their OS is using as many robust components from academia as possible while attempting to integrate them into something usable. They have a microkernel, a resource architecture, Nitpicker GUI, and so on. It needs help wherever people can get it.