libapache2-mpm-itk 2.4.7-02-1.1 (amd64 binary) in ubuntu wily

 The mpm-itk module, although not technically a Multi-Processing Module (MPM)
 (although it used to be) enhances the classical "prefork" module (that is,
 without threads), in such a way that it allows you to constrain each
 individual vhost to a particular system user and group. 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. mpm-itk is largely independent of e.g.
 what scripting technology is in use on your server; in particular, it does not
 require you to run your scripts as CGI to get the extra security benefit.