As attackers use automated methods to inflict widespread damage on vulnerable systems connected to the Internet, it has become painfully clear that traditional manual methods of protection do not suffice. This paper discusses an intrusion prevention approach, including its prototype, based on active networks that helps to provide rapid response to vulnerability advisories. We describe the design and implementation of the Intrusion Blocker based on Active Networks (IBAN), a vulnerability Scanner and intrusion blocker that can provide interim protection against a limited and changing set of high-likelihood or high-priority threats. It is expected that this mechanism would be easily and adaptively configured and deployed to keep pace with the ever-evolving threats on the Internet.