TCP Fin scans on my mac - help?

Okay so I don't know anything about it, but my sister who has control of the wireless router tells me my laptop is doing TCP fin scans or something. Only problem is, she says it is happening while my laptop's internet is offline. Is this possible? If the internet is disconnected, and my laptop is off (or asleep) is it possible for these TCP fin scans to occur? If it is, how do I stop it from happening? I realised my firewall on my mac was turned off so I turned it back on... what else do I do?