LBP and kids

Can anyone shed light on this for me or is it me being daft

Noticed the other day when the kids were playing under my profile that some total stranger had joined them, whilst I kept a close eye on them it did make me feel uncomfortable so I thought go through the options and only allow friends abit like the 360, couldn't find anything, the wife is really twitchy about this kind of stuff so i guess the question is how can I block everyone apart from friends? or can I make the game play in a "standalone mode"?

Thanks in advance

Chesser

the game gives the option on each world as play online
or play alone
my kids play all the time
i have not looked into the freinds & family side of things...
i will now.
only option for the moment if the wife is that twitchy...
disconect ps3 from the net till you get a better idea...