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.