Which source would be the best to determine if personal information of a CEO is available for sale?

The dark web is the most suitable source for determining if personal information of a CEO is available for sale. The dark web refers to parts of the internet that are not indexed by traditional search engines and often require specific software, configurations, or authorization to access. It is known for hosting illicit activities, including the trading of stolen personal information and other sensitive data. On platforms within the dark web, individuals can buy or sell personal information, credentials, and other compromised data.

While open-source intelligence can provide valuable information gathered from publicly available sources, it would not typically include sensitive or illegally obtained personal information being sold. Automated information sharing primarily deals with the exchange of data between organizations and systems, often for security updates and threat intelligence, rather than the sale of personal information. Vulnerability databases focus on identifying security flaws in software and hardware, and do not deal with the sale or availability of personal information.

This context highlights why the dark web stands out as the appropriate source for addressing concerns about the availability of a CEO's personal information for sale.