The practice described is Code review, which is a part of secure software development best practices. Code reviews are conducted to ensure that the code adheres to accepted coding patterns and meets the team's quality standards. This process involves the examination of source code by a person or a group other than the author to identify bugs, security vulnerabilities, and ensure compliance with coding standards.
References:
* Fundamental Practices for Secure Software Development - SAFECode1.
* Secure Software Development Framework | CSRC2.
* Secure Software Development Best Practices - Hyperproof3.

The secure coding best practice that emphasizes treating all incoming data as untrusted and subjecting it to validation is known as input validation. This practice is crucial for ensuring that a system only processes valid, clean data, thereby preventing many types of vulnerabilities, such as SQL injection, cross-site scripting (XSS), and buffer overflows, which can arise from maliciously crafted inputs.
* Input validation involves verifying that the data meets certain criteria before it is processed by the system. This includes checking for the correct data type, length, format, and range. It also involves sanitizing the data to ensure that it does not contain any potentially harmful elements that could lead to security breaches.
* A centralized input validation routine is recommended for the entire application, which helps in maintaining consistency and effectiveness in the validation process. This routine should be implemented on a trusted system, typically server-side, to prevent tampering or bypassing of the validation logic.
* It's important to classify all data sources into trusted and untrusted categories and to apply rigorous validation to all data from untrusted sources, such as user input, databases, file streams, and network interfaces.
By adhering to the input validation best practice, developers can significantly reduce the attack surface of their applications and protect against a wide array of common security threats.
References: The verified answer is supported by the Secure Coding Practices outlined by the OWASP Foundation1 and other reputable sources such as Coding Dojo2 and CERT Secure Coding3.

The phase being described is the Design phase of the SDLC. During this phase, developers and IT staff determine the architectural and operational details of the product, which includes decisions on how to deliver various components such as secure REST services, mobile apps, and web applications. The Design phase is crucial for setting the foundation for the development work that will follow, ensuring that the product will be secure, scalable, and maintainable.
References: The information aligns with the descriptions of the SDLC phases provided in resources such as GitHub's explanation of the SDLC1 and other industry-standard software development lifecycle resources234.

The privacy impact statement requirement that defines how personal information will be protected when authorized or independent external entities are involved is best categorized under Third party requirements.
This aspect of privacy impact assessments ensures that personal data is safeguarded even when it is necessary to involve third parties, which could be service providers, partners, or other entities that might handle personal information on behalf of the primary organization. These requirements typically include stipulations for data handling agreements, securitymeasures, and compliance checks to ensure that third parties maintain the confidentiality and integrity of the personal information they process.
References:
* Guide to undertaking privacy impact assessments | OAIC1
* A guide to Privacy Impact Assessments - Information and Privacy2
* Personal Information Protection Law of China: Key Compliance Considerations3
* Privacy Impact Assessment - General Data Protection Regulation (GDPR)4
* Privacy impact assessment (PIA) - TechTarget5

Manual code review is a type of security analysis that requires a significant time investment from a highly skilled team member. This process involves a detailed and thorough examination of the source code to identify security vulnerabilities that automated tools might miss. It is labor-intensive because it relies on the expertise of the reviewer to understand the context, logic, and potential security implications of the code.
Unlike automated methods like static or dynamic code analysis, manual code review demands a deep understanding of the codebase, which can be time-consuming and requires a high level of skill and experience.
References: The information provided here is based on industry best practices and standards for secure software design and development, as well as my understanding of security analysis methodologies12.