What is a "scraper" and why is that bad?
Historically, SCRAPER here on Stack Exchange meant "Stack Content Republishers Attributing Poorly and/or Excelling at Ranking." More generally, a scraper is another website which copies content from our sites either by scraping directly from our pages, accessing the information through our API, or some other means. In principle, there's actually nothing wrong with doing this. Our content is licensed under Creative Commons BY-SA 3.0 and is freely redistribituble, so long as they follow the attribution requirements and link back to us as the source. Some sites, however, do not follow these rules or bring up other concerns in the process.
When should I report these sites?
The site is a proxy. Whatever the purpose of the site actually is, malicious or not, proxies represent a serious security threat to our site. Sometimes they even start showing up in Google results and users click on them not realizing that they aren't actually on Stack Overflow. Users get confused, or try to log in and accidentally send sensitive information to a third-party service.
The site outranks us on Google. While you can report this directly to Google yourself (see below), it's nice to have these reports on file so we can investigate further and make sure there are no other problems we might need to check out.
The site doesn't follow attribution requirements. Oftentimes these sites will not listen to ordinary users, and will only respond to official requests directly from Stack Exchange. Sometimes these sites are also hard to contact, or may require more drastic measures which only Stack Exchange representatives are allowed to take. Please report these sites and include information about which attribution requirements they are not following.
The site uses a different license or claims ownership of the content. Our license terms require that any redistributed content be licensed under the same license.
When should I not report these sites?
They follow all the attribution requirements, and don't outrank us on Google. As mentioned before, there is nothing wrong with copying our content elsewhere on the web, so long as they are following all the attribution requirements given. If the site is not also outranking us on Google, then there is no real reason we need to know about it, since there isn't any action we can or need to take.
You landed on the malware page. We've already detected and thwarted quite a few sites, and when attempting to access them they will redirect you to this page on our network to notify you that the site is not the official site. You only need to contact us from this page if you think you landed there by mistake because you think the site you were attempting to access is blocked erroneously.
How do I go about reporting these sites?
Please contact us directly using the on-site form. Select the "Stack Exchange content is being reproduced without attribution" option from the drop-down, and provide as much information as possible. Even if you are reporting an entire site that is scraping many questions, please provide an example of a question on their site and the corresponding question on our site, as well as any Google search terms you used that led you to finding this site. Any other information you might have can be included in the free-form text box.
Can I do anything myself?
Absolutely! While larger cases of mass violations will require the Stack Exchange team's intervention, smaller cases where a user simply wasn't aware of our attribution requirements do not require us to get involved. If you see a blog post which copied our content and it's just a one-off deal, you should feel free to contact the author as a concerned member of the community. There is nothing wrong with a user pointing out the rules and hopefully getting an author to fix their content as well as educating them about our attribution requirements.
If you see copied content outranking us on Google, you can also report this directly to Google on your own so that they can immediately be aware of the problem and get our results back on top where they belong. Please keep in mind that this Google form is only for content outranking us - it is not for reporting scrapers in general. This form is no longer accepting submissions. It is unclear whether or not this is a permanent change.
If you've found a site proxying our content and serving malware, you can also report the site directly to Google using the spam report tool.
If the website contains Google AdSense ads, you can report their abuse of ads to Google. Other advertising networks may have similar report systems.
I am the author of a scraped post
If the CC-BY-SA requirements have not been met, your copyright has been violated.
This post won't give you legal advice on when exactly this is the case and what to do, but you can find some reputable advice from free culture organizations by searching for keywords like license violation, license termination and license enforcement.