Microsoft fax security

I recently installed and set up Microsoft fax to operate
via a modem connected to my PC. However, our network
administrator would not allow this, stating that this
could facilitate access to our network via this fax line
(my PC is also connected to a server) by unauthorised
persons. Could somebody please advise as to the extent of
the danger, if at all, and what could be done about it.

Thanks
Sindy (Johannesburg, South Africa)