defend from -> :() { :&:; } ;:

Matt datahead4 at
Mon Oct 22 14:57:56 PDT 2007

On 10/22/07, Martin Tournoij <carpetsmoker at> wrote:
> On Sun 21 Oct 2007 12:10, Danielisz Laszlo wrote:
> > Please do not try to execute this: :() { :&:; } ;: on your BSD machine.
> > I ask all who already tried it how to defend from this?
> Wow,, my machine just crashed :-/
> Does in this work on other OS's as well (ie. GNU/Linux)? Or just
> (Free?)BSD? I really don't feel like crashing another machine right
> now...
> Only works in sh, not in csh.
> Anyway, this seems to be security/stability issue, maybe a PR is in
> order?
> Regards,
> Martin Tournoij

I'm not a sh or bash syntax expert, but isn't this a standard "fork
bomb" type command?  If so, it should be possible to mitigate it with
sensible login tunings set in login.conf (in this particular case, I
think "maxprocesses" is the one to focus on).

Executing this command on my workstation does not result in any
(noticeable) bad side effects under sh or bash login shells - just
notifications of "Cannot fork: Resource temporarily unavailable" as
the max process limit is hit.

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