Five Rivers is hosted by Yahoo Inc. Shopping cart security is managed by them through their servers.

Here is an excerpt from their site:

Credit Card Security

At Yahoo, we make every effort to keep your personal information, including your credit card number, totally secure.

We use Secure Socket Layer (SSL) encryption which is supported by most browsers. If your browser doesn't support SSL, we won't allow you to continue with your reservation. As you enter your credit card number, SSL encodes it so it is transmitted in a format that prevents eavesdropping or data theft. When it's received by our secure server, your credit card number is never transmitted over the Internet again.