Wow.. I just got back from my offline job and read about this... ok.. I've just logged in the site right now and so far it all seems normal for me.
However if you noticed such a bandwidth increase then either someone is promoting ConstantBux at a pretty large scale probably using any hosted images on your site such as banners, splash pages etc. Images are the most usual reason for a crazy increase in bandwidth usage.
But fist things first.. you may need to know if too much traffic is received from one single computer or a group of computers.
Buxhost offers you some options to observe logged traffic so log in to your administration panel and check out the following :
1. Click on Website Statistics and then Visitors at the bottom of the left link list.
See how huge the change was during the last few days and below you can check if a specific country
stands out of the rest with very huge difference in the traffic amounts you are receiving from it..
2. Click on Traffic Log (back in the main menu) and click on "Download Log" in .txt format (it's much easier to read than excel).
Now scroll down to the days of the increased activity and try to notice if there is an IP that is repeatedly showing up many many times in a row or sth. You may need to spend some time on this to really find something interesting. If you spot any, then copy the whole content of the log file to word and search for that IP address. Word 2010 immediately lets you know how many occurencies have been found in the document. If you spot any one having a couple of tenths of thousands within a day or something then you probably have a suspect.
3. There are some blacklists of IP addreses from spammers you can also use spot if an IP belongs to a known spammer.
One of the best that I've used a lot for my forum is :
http://www.stopforumspam.com/If you enter any abusing IP address that is in their list and search for it, it will show you more details, related nicknames, emails and information on the spamming IP address etc.
Then after having such info collected you might want to check your site for a member associated with that IP address and contact them for some explanation regarding their activity. However they may be simply work
advertising your site which is actually good so don't rush to jump into conclusions.. but since there was not much of an increase in the number of total members of the site I don't think that would be the case this time.
Let me know if you find anything interesting or need help with something..