Both Google and Facebook have implemented robust security measures to protect their source code, even with hundreds of staff members having access to it. Here are some ways they keep their source code secure:

Access Control: Both companies use access control mechanisms to limit access to source code to only those employees who need it to perform their job duties. This is typically enforced through a combination of role-based access control, multi-factor authentication, and strict permission policies.

Code Reviews: Before any code is committed to the source code repository, it must go through a rigorous code review process. This helps to catch any potential security vulnerabilities or code errors before they are merged into the main codebase.

Monitoring and Logging: Both companies have robust monitoring and logging systems in place to detect any unusual activity, such as unauthorized access attempts or suspicious behavior by employees.

Encryption and Segmentation: Both companies use encryption and segmentation techniques to protect their source code from unauthorized access. For example, the source code may be split into smaller parts and distributed across different servers or data centers, with each part encrypted separately.

Regular Audits: Both companies regularly audit their source code repositories to ensure that all access is logged, and any unauthorized access attempts are detected and investigated promptly.

Overall, both Google and Facebook take the security of their source code very seriously and have implemented multiple layers of protection to ensure that it remains secure even with hundreds of staff members having access to it.