This is just a guide - the wording on my actions are in no way legally binding, but written for suggestion - read on :)
As a collector it alarms me the number of items that I have found to be fakes on eBay, this site is awash with them - the best way to protect against purchasing a fake item is to ask the seller straight out: 'can you confirm this item is 100% authentic, genuine Hugo Boss', do consider the response carefully and the way inwhich it is worded, such as 'this is 100% Hugo' or 'yes this is authentic HB', if you don't get a response your question in effect has been answered. Please also note some Top Sellers are not above trying to pass fake goods, be extra cautious here.
I recommend that you always purchase through PayPal for buyers protection. Do note a seller may find ways to shut down their account thus suspending any refund that you are due - this has happened to me. By far the greatest protection is if you're in any doubt, do not purchase!