When you connect to the Internet, you are going to be scanned and attacked--but you can fight back and win. The key: Be consistent and methodical in your response. Keep current on patching, implement sound network-configuration practices, and keep up to date on current dangers. These organizations can help:
CAIDA: The Cooperative Association for Internet Data Analysis is a group of commercial, government and research entities working to build a robust and scalable global Internet infrastructure.
ICAT Metabase: A searchable index on computer vulnerabilities, ICAT provides very granular search capabilities and links to vulnerabilities and patch information.
ISS Security Center: Security tools vendor Internet Security Systems' X-Force security intelligence is touted as the No. 1 security advisory, representing 45 percent of all vulnerabilities discovered by commercial research entities.
Security Focus: Owned by Symantec, the SecurityFocus site hosts the Bugtraq mailing list and a forum for security experts to discuss new IT threats and attacks as well as ways to prevent security breaches.