questions on transportation

[Ms Mo Me]

No: HPFGUIDX 131174

<Geoff:
<I don't see why this is odd?

<Using a portkey and using the fireplace Floo network
<to speak to 
<someone (rather than travelling there) seems to
<happen in a number of 
<places, why not Hogwarts?

<Surely the only thing which cannot be achieved in
<and out of the school 
<is Apparating?

<Perhaps I am missing the thrust of your question?


Oops, I'm sorry, I didn't make my question clearer. 
The reason I find it odd is because Sirius says he
broke into someone's house to use their fireplace. 
That would essentially mean, that any wizard could use
any floo fireplace and get into Hogwarts without any
security measures.  Essentially, any death eater could
easily enter the Gryffindor common room at any time. 
Or, they could use an unauthorized portkey to get
there.  Which had me wondering, I haven't seen any
security restrictions on any of these... why not?

~Mo