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One weakness of a vulnerability scanner is that it is not designed to go through filters or bypass security controls like firewalls or intrusion detection systems. Vulnerability scanners typically perform well in identifying known weaknesses within the perimeter of a network or system but might not effectively assess systems that are shielded by robust security measures, which can filter out the scanner's attempts to probe or attack.References:

National Institute of Standards and Technology (NIST), "Technical Guide to Information Security Testing and Assessment".

A vulnerability that is exploited before the vendor has issued a patch or even before the vulnerability is known to the vendor is referred to as a "zero-day" vulnerability. The term "zero-day" refers to the number of days the software vendor has had to address and patch the vulnerability since it was made public—zero, in this case.References:

Symantec Security Response, "Zero Day Initiative".

IPsec uses two main protocols to secure network communications: Authentication Header (AH) and Encapsulating Security Payload (ESP).

Both AH and ESP use a Security Parameters Index (SPI), which is a critical component of their headers. The SPI is a unique identifier that enables the receiver to select the correct security association for processing incoming packets.

AH provides authentication and integrity, while ESP provides confidentiality, in addition to authentication and integrity. Both protocols use the SPI to manage these functions securely.

References

"IPsec Security Architecture," RFC 4302 (AH) and RFC 4303 (ESP).

"IPsec Explained," by Juniper Networks.

In the configuration of Microsoft Windows Firewall with Advanced Security, you can define IPsec rules as part of your security policy. Typically, these rules can be organized into four main categories: Allow connection, Block connection, Allow if secure (which can specify encryption or authentication requirements), and Custom. While the interface and features can vary slightly between Windows versions, four fundamental types of rules regarding how traffic is handled are commonly supported.References:

Microsoft documentation, "Windows Firewall with Advanced Security".