During a passive reconnaissance exercise, you want to gather historical data about the target's web application that may disclose previous security postures or vulnerable configurations. Which of the following sources would be BEST for obtaining this information?
Inspecting the current robots.txt file to infer past web structure
Using the Wayback Machine to review snapshots of the website at different points in time
Performing a DNS lookup to find historical IP addresses associated with the website
Using social media scraping to gather previous posts about the web application