The president of my company said to me this morning that one of our more tech-savvy customers mentioned a vulnerability that is brand new and something we need to worry about since there is obviously no protection against it yet.

We have our web site hosted by our local ISP and the server is the host to countless other web sites. He believes that if one of the other sites on that server is compromised then the hacker will be able to do whatever he/she wants to our site.

First of all, this doesn't sound like something new... is it? If the idea isn't new, how feasible is it for a hacker to compromise a server like that? The ISP is fairly big and professional and has a good number of customers unlike the guy that runs the ISP out of his basement down the street so I would think that they, if anyone, would know about this.

I'm planning on talking to the ISP directly about this but I'm sure that they'll play it down just to reassure me that our site is safe. I need the truth, not propaganda.