Unauthorised switchport access

[gary.shaw () dfpni gov uk]

Guys

I am responsible for several LANs that include sharing WCs with other organisations, and therefore access to my 3750 
switches in unlocked cabinets. 
I have no port security enabled and the ports are not shut down. 
I would like to know the security implications of having unused switchports available to anyone eg with a laptop & DHCP 
configured? 
Are there any simple pentests i could complete myself?
Is my organisation's network a sitting duck??
Thanks in advance!

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