It looks like they aggregate from multiple sources (more than just SO).
Here's an example SO-scraped page:
According to the other SO question Bobby referred to in the comments, looks like they're violating pretty much everything attribution-wise:
Visually indicate that the content is from Stack Overflow, Meta Stack Overflow, Server Fault, or Super User in some way. It doesn’t have to be obnoxious; a discreet text blurb is fine.
Hyperlink directly to the original question on the source site (e.g., https://stackoverflow.com/questions/12345)
Not a direct hyperlink; redirects through one of their pages.
Show the author names for every question and answer
Hyperlink each author name directly back to their user profile page on the source site (e.g., https://stackoverflow.com/users/12345/username)
Looking at this answer,
bigresource.com is already in the list of clones violating the attribution requirements.