The theHarvester tool is a Python script that searches through popular search engines and other sites for email addresses, hosts, and sub-domains.

Using theHarvester is relatively simple, as there are only a few command switches to set. The options available are as follows:

• -d: This identifies the domain to be searched; usually the domain or
  target's website.
• -b: This identifies the source for extracting the data; it must be one of
  the following: Bing, BingAPI, Google, Google-Profiles, Jigsaw, LinkedIn, People123, PGP, or All.
• -l: This limiting option instructs theHarvester to only harvest data from a specified number of returned search results.
• -f: This option is used to save the final results to an HTML and an XML file. If this option is omitted, the results will be displayed on the screen, and not saved.

The following screenshot provides the sample data extract from theHarvester for the packtpub.com domain: