I have been using this tool for about 2 weeks now and i havent found any faults with it.https://addons.mozilla.org/en-US/firefox/addon/5571
This add on basically puts a bid (you select how much) at say 6 seconds before an auction ends(or however many seconds you select), and the addon will bid on your behalf even if your not on the internet when it ends.
What is auction sniping?
Auction sniping is a process of placing your bid at last seconds.
Is sniping legal?
Yes, sniping is legal. Any bid placed within dedicated time frame (while auction is not ended) is perfectly legal.
Do I need to keep my Firefox running to snipe?
Your snipe will be done by the remote server which is up 24/7.
You can set your snipe and turn off your PC.
Please note i am no way affiliated with this product or website.