apache2-mpm-itk 2.2.16-6ubuntu2 (i386 binary) in ubuntu natty

 The ITK Multi-Processing Module (MPM) works in about the same way as the
 classical "prefork" module (that is, without threads), except that it allows
 you to constrain each individual vhost to a particular system user. This
 allows you to run several different web sites on a single server without
 worrying that they will be able to read each others' files. This is a
 third-party MPM that is not included in the normal Apache httpd.
 .
 Please note that this MPM is somewhat less tested than the MPMs that come with
 Apache itself.