How to fight JKH ( Japanese Keyword Hack )

We performed many site checks lately, which resulted in a JKH ( Japanese Keyword Hack ) case.
So I decided to write a short guide on how to sort JKH the right way.

To resume, here are the main steps:

1. Perform website backup ( site files and database ). If you can’t do it, contact your web hosting provider.
2. Signup with Google search console:
a) Add property and verify ownership.
b) Check if the are any security-related issues.
c) Remove newly created accounts from Search Console.
3. Search for your site on Google by entering site:your_site, where “your_site” is your site’s domain name. For example,
If you notice Japanese characters, your website is affected by JKH.
a) If search results is under 1,000 then the recovery process should take less.
b) If there are over 10,000 spam entries your site might experience difficulties ( timeouts, 500 errors, etc ). That’s because your website will be bombarded with crawl requests from various search engine bots (Bing, Google, Moz, etc).
Important! Host support might suspend your hosting account for excessive bandwidth usage. If you’re using WordPress, you can add this code inside header.php ( theme file ).

if (is_404()) { 
    echo "Ah! This page doesn't exist.";
    exit(); }

Otherwise, make sure your 404 page is custom having minimum size ( ~2KB ).
4. Perform a malware cleanup, making sure there are no infected files left.
If you use a CMS ( WordPress, Joomla or Drupal ), reinstall all the core files, as well as anything you may have added (such as themes, modules, plugins) – this way you’ll make sure all infected files are left behind.
5. Ask Google for a re-index
More details:
a) If your website is slow, lower crawl rate:
b) submit a legitimate sitemap file, which contain legitimate URLs: