Definition
The Japanese Keyword Hack is a type of SEO-oriented cyberattack where hackers compromise a website to automatically inject thousands of pages containing Japanese text, usually related to counterfeit products, online casinos, or pharmaceutical sites. Hackers exploit security flaws (outdated CMS, vulnerable plugins, weak passwords) to create these pages that leverage the hacked domain's authority to rank in Japanese search results. The site owner often sees nothing abnormal because the content is invisibly injected, sometimes via cloaking. Detection usually occurs through Google Search Console flagging Japanese indexed pages, or a site: search revealing thousands of unknown pages. Cleanup requires a complete technical intervention including software updates, password changes, and malicious code removal.
Key Points
- A hack exploiting domain authority to rank Japanese spam
- Often invisible to the site owner because content is hidden via cloaking
- Detection via Search Console, site: search, or Google security alerts
- Full cleanup requires updates, password changes, and code audit
Practical Examples
Detection via Google Search Console
A WordPress site owner discovers in Search Console that 5,000 Japanese pages have been indexed under their domain, with titles containing Japanese characters and links to counterfeit shops.
Exploiting a vulnerable plugin
Hackers exploit a flaw in an outdated WordPress plugin to inject a PHP script that dynamically generates Japanese pages visible only to search engines.
Impact on rankings
A business site loses 60% of its organic traffic as Google begins associating the domain with Japanese spam and degrades the ranking of all legitimate pages.
Frequently Asked Questions
Do a Google search with 'site:yourdomain.com' and check for Japanese pages you did not create. Also check Google Search Console for security alerts or an abnormally high number of indexed pages. The URL inspection tool can reveal hidden content.
Immediately put your site in maintenance mode, update the CMS and all plugins, change all passwords (FTP, database, admin), find and remove injected malicious PHP files, clean the database, then request a review in Search Console after resolving security alerts.
Go Further with LemmiLink
Discover how LemmiLink can help you put these SEO concepts into practice.
Last updated: 2026-02-07