You can safely assume that you are potentially at risk if you connect your system to the Internet. Your gateway to the Internet is your greatest exposure, so we recommend the following:
The gateway should not run any more applications than are absolutely necessary.
The gateway should strictly limit the type and number of protocols allowed to flow through it (protocols potentially provide security holes, such as FTP and telnet).
Any system containing confidential or sensitive information should not be directly accessible from the Internet.