Final answer:
To minimize his organization's digital footprint and reduce information exposure, Charles should enforce authentication on his organizational website, restricting public access to sensitive data. This action addresses the primary concern of safeguarding against potential attackers during passive reconnaissance.
Step-by-step explanation:
Charles wants to limit what potential attackers can gather during passive or semi-passive reconnaissance activities. Among the listed actions, limiting information available via the organizational website without authentication would typically reduce his organization's footprint the most.
While using a secure domain registration, limiting technology references in job postings, and purging all document metadata before posting are also measures that can minimize the exposure of sensitive details, the most comprehensive approach is to control access to organizational data. Security breaches, like those at major retailers and financial institutions, exemplify the risks associated with freely accessible personal and corporate information. By enforcing authentication, Charles's organization would prevent indiscriminate access to information, which is particularly vital given the increasing concerns about online privacy and the rising number of internet users worried about personal data exposure.