Social Information
For social engineering, it's useful to have information about the employees, their roles, contact information, operating system, browser, plugins, software, etc. Some resources are:
1) Google
Here as well, it's the most useful tool.
2) theHarvester and recon-ng
I already mentioned them in the previous section, but they have a lot more functionality. They can find a lot of information quickly and automatically. It's worth reading all their documentation.
3) LinkedIn
A lot of information about the employees can be found here. The company's recruiters are the most likely to accept your connection requests.
4) Data.com
Previously known as jigsaw. They have contact information for many employees.
5) File Metadata
A lot of information about employees and their systems can be found in metadata of files the company has published. Useful tools for finding files on the company's website and extracting the metadata are metagoofil [1] and FOCA [2].
[1] https://github.com/laramies/metagoofil [2] https://www.elevenpaths.com/es/labstools/foca-2/index.html