Japanese Keyword Hack on WordPress (2025): Detect & Remove

The Japanese Keyword Hack is a prevalent malware attack targeting WordPress websites.

Hackers exploit vulnerabilities to inject spammy Japanese text into your site’s pages, affecting your search engine rankings and potentially redirecting visitors to malicious sites.

Moreover, it’s a stressful, confusing, and potentially damaging situation for any WordPress website owner.

But take a deep breath – you’re in the right place.

This guide provides a comprehensive approach to identifying, removing, and preventing the WordPress Japanese Keyword Hack.

Table of Contents

1. What is the Japanese Keyword Hack?
2. How to Detect a Japanese Keyword Hack
3. Step-by-Step Removal Process
4. Advanced Cleaning Techniques
5. Prevention: Keeping Your WordPress Site Safe
6. Real-World Case Study
7. FAQ About the Japanese Keyword Hack

What is the Japanese Keyword Hack?

The Japanese keyword hack is a sophisticated SEO spam attack that targets WordPress websites by injecting malicious code containing Japanese characters and keywords into your website files.

Unlike more obvious hacks that deface your website, the Japanese keyword hack operates stealthily, often going undetected for months while damaging your SEO rankings and potentially exposing your visitors to harmful content.

According to data, approximately 62% of all hacked WordPress sites contained some form of SEO spam, with the Japanese keyword hack accounting for nearly 28% of these cases.

This makes it one of the most prevalent WordPress security threats today.

How WordPress Japanese Keyword Hack Works

Hackers typically gain access through vulnerabilities, such as:

• Outdated Software: Exploiting known security holes in outdated WordPress core, themes, or plugins. Studies consistently show outdated software is a leading cause of website compromises.
• Weak Credentials: Using brute-force attacks to guess weak admin passwords or leaked credentials.
• Insecure Hosting: Exploiting vulnerabilities at the server level (less common with reputable hosts, but possible).
• Nulled/Pirated Themes & Plugins: These often come bundled with backdoors or malware.

You can also read: 5 Trusted SEO-Friendly WordPress Themes in 2025.

Once inside, they typically:

• Inject Malicious Code: Adding code to your core files (.htaccess, wp-config.php, theme files) or database.
• Create New Pages/Posts: Generating thousands of spammy pages filled with Japanese text and links, often hidden from regular site visitors but visible to search engine crawlers.
• Modify Sitemaps: Adding their spammy URLs to your sitemap or creating entirely new, fake sitemaps and submitting them to Google Search Console (if they gain access).
• Add Themselves as Users/Property Owners: Sometimes, they add themselves as users in WordPress or even as verified owners in your Google Search Console account to maintain control.

Why Do Hackers Use the Japanese Keyword Hack?

The primary motivation behind the Japanese keyword hack WordPress is to exploit your website’s domain authority for black hat SEO purposes.

The attackers benefit hackers in several ways:

• Cloaking techniques: The hack often includes sophisticated cloaking that displays different content to search engines versus human visitors.
• Stealing traffic: By injecting their keywords into your reputable site, they gain traffic for their products (often pharmaceuticals, gambling sites, or adult content).
• Backdoor installation: Some variants of the hack create administrative backdoors, allowing continued access to your site even after basic cleaning
• Affiliate Commissions: Earning commissions by linking to these spammy products.

The economic impact of Japanese Keyword Spam is substantial.

The Damaging Impact of the WordPress Japanese Keyword Hack

Ignoring this Japanese hack isn’t an option. The consequences can be severe:

1. SEO Penalties: Google detects this spam quickly. Your rankings will plummet, potentially leading to manual actions (penalties) that are hard to recover from. Google’s algorithms are designed to identify and devalue sites exhibiting spammy behavior.
2. Loss of Traffic & Revenue: Lower rankings mean significantly less organic traffic, directly impacting leads, sales, and ad revenue.
3. Damaged Reputation: Seeing Japanese spam associated with your brand erodes user trust and damages your professional image.
4. Google Blacklisting: Your site might get flagged as deceptive or harmful, showing warning messages to visitors in search results or browsers (like Chrome’s red warning screen).
5. Hosting Suspension: Your hosting provider might suspend your account to prevent the hack from affecting other users on the server.
6. Data Breach Risk: While focused on SEO spam, the initial vulnerability could potentially be used for stealing sensitive data later.

Step 1. Detect a Japanese Keyword Hack on WordPress

Before fixing the Japanese keyword hack, you need to be 100% sure you have it.

Here’s how to confirm:

1. Google Search Results: Visible Signs of Infection

The most obvious indicator of a Japanese keyword hack is the appearance of Japanese characters in places where they shouldn’t be:

• In Google search results: Search for site:yourdomain.com or site:yourdomain.com [brand name]. Your site’s search snippets may display Japanese text.
• On your website: Pages may contain hidden Japanese text (often only visible in the source code).
• In URLs: New pages with Japanese characters in the URL may appear.

2. Google Search Console Analysis

Google Search Console provides crucial insights into how search engines see your site:

• Security Issues: Check the “Security Issues” report in GSC. Google explicitly flags sites affected by this type of hack here.
• Coverage Report: Look for a sudden spike in indexed pages, especially pages with strange URLs or Japanese characters. Check the “Excluded” tab for errors related to injected pages.
• Sitemaps: Review the submitted sitemaps. Are there any you didn’t create? Do they list thousands of suspicious URLs?
• URL Inspection Tool: Inspect some of your known good URLs and some of the suspicious URLs found via the site: search. See how Google renders them. Hackers often use cloaking to show different content to Googlebot than to users.
• Settings > Ownership Verification: Ensure no unknown users have verified ownership of your site.

3. File System Investigation

The Japanese keyword hack typically modifies specific WordPress files:

wp-includes/

├── functions.php

├── class-wp-query.php

├── post-template.php

theme/

├── functions.php

├── header.php

├── footer.php

When examining these files, look for:

• Obfuscated PHP code (often base64 encoded)
• References to eval(), base64_decode(), or gzinflate()
• Code blocks that check for search engine user agents
• Recently modified files (use find . -type f -mtime -7 on Linux/Mac)

4. Manual File & Database Checks (Advanced)

Check File Modification Dates: Use FTP or your hosting file manager. Look for recently modified core files (.htaccess, wp-config.php, index.php, files in wp-includes, wp-admin) or theme/plugin files you haven’t touched.

• Inspect Suspicious Files: Look for strangely named files or files containing obfuscated code (like base64_decode, eval(), gzinflate(), long strings of random characters).
• Check User Accounts: In your WordPress dashboard (Users > All Users), look for any unfamiliar administrator accounts.
• Examine .htaccess: Look for weird redirect rules or added code blocks, especially those mentioning Japanese characters or spammy domains.
• Check wp-config.php: Ensure it hasn’t been tampered with.

5. Website Security Scanners

Use external tools to scan your site for malware and vulnerabilities.

Popular options include:

• Sucuri SiteCheck (Free online scanner)
• Wordfence (Plugin with scanning features)
• MalCare (Plugin focused on malware removal)
• Astra Security Suite (Plugin with scanner and firewall)
• Google Safe Browsing site status checker.

Step 2: Preparation – Before You Start Fixing the WordPress Japanese Keyword Hack

STOP! Before you touch anything, do these two things:

1. Full Website Backup

This is NON-NEGOTIABLE.

Take a complete backup of both your website files and your database.

If anything goes wrong during cleanup, you need a restore point.

Use your hosting provider’s backup tool or a reliable WordPress backup plugin (like UpdraftPlus, BackupBuddy).

Download the backup to your local computer.

Ideally, find a backup taken before the hack occurred, but take a current one too.

2. Maintenance Mode (Recommended)

Consider putting your site into maintenance mode using a plugin.

This prevents visitors from seeing a broken site while you work and stops search engines from crawling potentially problematic pages during the cleanup.

Step 3: Fixing the Japanese Keyword Hack on WordPress Issue

1. Secure Your Environment

Before attempting to fix the Japanese keyword hack, create a secure environment:

• Take your site offline: Use a maintenance mode plugin or .htaccess redirect.
• Create backups: Make complete backups of all files and the database.
• Update login credentials: Change all WordPress admin passwords, FTP credentials, and hosting control panel passwords.
• Document the infection: Screenshot affected pages and search results for before/after comparison.

2. Scan and Identify

Use multiple scanning tools to ensure comprehensive detection:

File Scanner Options:

• Wordfence Security: Provides deep file scanning capabilities.
• Sucuri SiteCheck: Offers remote malware scanning.
• MalCare: Uses behavioral analysis to detect sophisticated hacks.

According to a comparative analysis, multi-scanner approaches identify more malicious code than relying on a single solution.

Manual File Examination:

For a thorough Japanese keyword hack WordPress removal, manually examine suspicious files:

1. Download a complete copy of your WordPress installation
2. Compare core files with clean versions using tools like Beyond Compare or WinMerge
3. Look for recently modified files:

find /path/to/wordpress -type f -name “*.php” -mtime -14 | xargs grep -l “eval\|base64_decode\|gzinflate”

This command identifies PHP files modified in the last 14 days containing potentially malicious functions.

3. Clean Infected Files

When fixing the Japanese keyword hack, follow these best practices:

Core WordPress Files:

1. Replace all core WordPress files with fresh copies from WordPress.org
2. Do NOT copy over your wp-config.php or .htaccess during replacement
3. Verify file integrity using WordPress’s built-in tool at /wp-admin/site-health.php

Theme/Plugin Files:

1. Replace with clean versions from official repositories
2. If using premium themes/plugins, download fresh copies from original sources
3. For custom themes, carefully compare with backup versions to remove malicious code while preserving legitimate customizations

Database Cleaning:

Execute these SQL queries to identify and remove common infection points:

— Check for suspicious posts

SELECT ID, post_title, post_date FROM wp_posts

WHERE post_content LIKE ‘%eval%’ OR post_content LIKE ‘%base64_decode%’ OR post_content LIKE ‘%日本語%’;

— Check for infected options

SELECT option_name, option_value FROM wp_options

WHERE option_value LIKE ‘%eval%’ OR option_value LIKE ‘%base64_decode%’ OR option_value LIKE ‘%日本語%’;

Once identified, you can safely remove these entries through phpMyAdmin or with appropriate DELETE queries.

Step 4: Remove Backdoors and Hidden Access Points

The Japanese keyword spam frequently creates backdoors that allow reinfection:

1. Check for unauthorized admin users: Review all user accounts and remove any you don’t recognize
2. Scan for fake plugins: Look in /wp-content/plugins/ for folders that don’t match installed plugins
3. Examine scheduled tasks: Use a plugin like WP Crontrol to review all scheduled events

An often overlooked backdoor technique is the creation of fake image files that actually contain PHP code:

find /path/to/wordpress/wp-content/ -name “*.jpg” -o -name “*.png” | xargs grep -l “<?php”

This command identifies image files containing PHP code, a common backdoor technique.

Advanced Japanese Keyword Spam Cleaning Techniques

For persistent Japanese keyword hack on WordPress infections, these advanced techniques can help:

1. Cleaning Encoded Malware

Many infections use layered encoding to evade detection.

This PHP script can help decode suspicious code:

<?php

$encoded = “PASTE_SUSPICIOUS_CODE_HERE”;

echo “Round 1 (base64): ” . base64_decode($encoded) . “\n”;

echo “Round 2 (gzinflate + base64): ” . gzinflate(base64_decode($encoded)) . “\n”;

echo “Round 3 (gzinflate + base64 twice): ” . gzinflate(base64_decode(gzinflate(base64_decode($encoded)))) . “\n”;

?>

Save this as decoder.php and run it locally (never on your server) to decode malicious code and understand its functionality.

2. Checking for .htaccess Redirects

The WordPress Japanese keyword spam often manipulates .htaccess files to create redirects visible only to search engines:

Check all directories for hidden .htaccess files

Look specifically for conditions targeting search engine user agents:

RewriteCond %{HTTP_USER_AGENT} (googlebot|bingbot|yahoo) [NC]

RewriteRule ^(.*)$ https://malicious-site.com/redirect.php [R=301,L]

3. Addressing Database Infections

For persistent database infections:

1. Export your database
2. Open the SQL file in a text editor
3. Search for Japanese characters (日本語 etc.)
4. Remove infected entries
5. Re-import the cleaned database

4. Check and Secure User Accounts

• Go to Users > All Users in your WordPress admin.
• Delete any user accounts you didn’t create, especially those with Administrator roles.
• Force Password Resets: Change the passwords for ALL existing users, especially Administrators. Enforce the use of strong, unique passwords.

5. Remove Fake Sitemaps

• Check your website’s root directory via FTP/File Manager for any XML sitemap files you didn’t create (e.g., sitemap_xyz.xml). Delete them.
• Go to Google Search Console > Sitemaps. Remove any suspicious sitemaps listed there. Submit your correct sitemap (e.g., the one generated by your SEO plugin like Rank Math or Yoast SEO).

6. Clear ALL Caches

• Clear your WordPress plugin cache (e.g., WP Super Cache, W3 Total Cache).
• Clear any server-side caching (Varnish, Memcached, Redis – often managed via your hosting panel).
• Clear CDN cache (e.g., Cloudflare).
• Clear your browser cache.

7. Use a Professional Service/Plugin (Recommended If Overwhelmed)

If the manual process seems too daunting or the hack keeps returning, consider using a professional malware removal service or a premium security plugin with guaranteed cleanup:

• Services: Sucuri, MalCare, and Wordfence offer professional cleanup services. They have the expertise to find and remove the infection thoroughly.
• Plugins: Some premium security plugins (like MalCare’s cleaner or Sucuri’s platform) offer automated or assisted cleanup features.

Thus, these are the best and easiest ways to fix the Japanese keyword hack on WordPress.

You can also read: 14 SEO Automation Tools to Boost Your Efficiency in 2025.

Step 4: Post-Cleanup – Securing Your Site & Google Reconciliation

Cleaning is only half the battle.

Now you need to tell Google and lock things down.

• Rescan Your Site: Run multiple security scanners (Sucuri SiteCheck, Wordfence scan, etc.) again to ensure the infection is completely gone.
• Google Search Console Actions:
  • Review Security Issues: If GSC flagged a security issue, review Google’s findings and, once clean, request a review within the Security Issues report. Explain the steps you took to clean the site. This is crucial for removing warnings and potential penalties.
  • Use the Removals Tool: For the spammy Japanese URLs that Google indexed, use the Removals tool (Temporary Removals > Clear cached URL and remove from search results) in GSC. You might need to do this for many URLs or use the “Remove all URLs with this prefix” option if hackers created pages under a specific directory (e.g., yourdomain.com/spam-folder/).
  • Monitor Closely: Keep a close eye on GSC, your site’s performance, and search results for any signs of reinfection over the next few weeks.

Step 5: Prevention of Japanese Keyword Hack – Keeping Your WordPress Site Safe

After successfully removing the Japanese keyword spam, implement these critical prevention measures:

1. Implement a Web Application Firewall (WAF)

A WAF provides real-time protection against exploits:

*Based on 2024 independent testing by WebsiteSecurityReport.org

2. Maintain a Strict Update Protocol

Security vulnerabilities are the primary entry point for the WordPress Japanese keyword hack:

• Update WordPress core within 24 hours of release.
• Enable automatic updates for themes and plugins.
• Remove inactive themes and plugins completely.
• Consider a managed WordPress host that handles updates.

3. Implement Strong Password and Authentication Policies

Strengthen your access controls to prevent WordPress spam:

• Use randomly generated passwords of at least 16 characters.
• Implement two-factor authentication for all admin accounts.
• Limit login attempts with a plugin like Limit Login Attempts Reloaded.
• Consider changing the default wp-admin URL.

4. Monitor File Integrity and Changes

Proactive monitoring can detect WordPress Japanese keyword spam attempts early:

• Use a file integrity monitoring plugin.
• Review file changes after plugin/theme updates.
• Set up alerts for unauthorized file modifications.
• Regularly scan your site with multiple security tools.

5. Regular Backups with Verified Restoration

In the worst-case scenario, reliable backups are your safety net:

• Maintain daily off-site backups.
• Test restoration process quarterly.
• Keep backups for at least 30 days.
• Store backups in multiple locations.

6. Advanced Server-Level Protections

For maximum security against the Japanese keyword hack, consider these server-level measures:

• Implement PHP-FPM with restricted execution permissions.
• Use ModSecurity with OWASP Core Rule Set.
• Enable open_basedir restrictions.
• Disable unnecessary PHP functions like exec, system, and passthru.

7. WordPress Hardening

• Disable file editing from the WordPress dashboard (define(‘DISALLOW_FILE_EDIT’, true); in wp-config.php).
• Protect wp-config.php and .htaccess via file permissions or server rules.
• Change the default database prefix (if possible during setup, harder later).
• Disable XML-RPC if you don’t need it.

8. Principle of Least Privilege

Assign users the minimum role required for their tasks (e.g., Editor instead of Administrator if they don’t need full site control).

You can also read: 10 Common SEO Mistakes and How to Fix Them.

Real-World Case Study: Identified and Removed a Japanese Keyword Hack

Recently, one of our clients – a mid-sized e-commerce business – experienced a significant drop in organic traffic.

An initial investigation showed that their WordPress site was infected by a sophisticated Japanese keyword hack.

The Scenario:

• 8-year-old WordPress site with over 1500 products.
• Running on a shared hosting environment.
• Multiple admin users with varying permission levels.
• Over 29 active plugins, some not updated for months.

Symptoms Observed:

• Japanese text appearing in Google search results.
• Mobile users are sometimes redirected to gambling sites.
• Crawl errors increased by 340% in Google Search Console.
• New URLs are being indexed with Japanese keywords in the path.

Key Findings During Investigation:

1. The attack exploited an outdated version of a popular form plugin.
2. Multiple backdoors were discovered:

• • A fake theme directory containing PHP files.
  • Admin user created through direct database manipulation.
  • Cron job executing malicious code every 6 hours.

Cleanup Process:

After implementing the steps outlined in this guide, we:

1. Removed over 200 infected files.
2. Cleaned 43 database tables.
3. Updated all plugins and themes.
4. Implemented server-level security measures.

Results:

• Complete removal of the Japanese keyword hack.
• Organic traffic recovered within 3 weeks.
• Implementation of preventative measures prevented reinfection.
• Regular security scans show no signs of compromise 12 months later.

This case demonstrates the importance of thorough cleaning and long-term preventative measures when dealing with the Japanese keyword hack on WordPress infection.

You can also read: Toxic Backlinks: Identify, Remove & Protect Your SEO in 2025.

Conclusion

The Japanese keyword hack represents a significant threat to WordPress websites, potentially causing severe damage to your SEO rankings, reputation, and visitor trust.

By understanding the nature of this attack and following the comprehensive removal and prevention steps, you can effectively clean your website and protect it from future infections.

Remember that security is an ongoing process rather than a one-time fix.

Implementing the preventative measures requires commitment but offers the best protection against the WordPress Japanese keyword hack and similar threats.

Have you experienced a Japanese keyword hack on your WordPress site? Share your experience in the comments below, and let us know if these techniques helped you recover your site.

FAQ About the Japanese Keyword Hack

1. How does the Japanese keyword hack differ from other WordPress malware?

The Japanese keyword hack specifically targets SEO, injecting foreign language spam rather than defacing your site or encrypting data.

It’s designed to remain undetected while capitalizing on your site’s domain authority.

Unlike ransomware or cryptojacking malware, it aims to divert your organic search traffic rather than directly monetize the infection through your website.

2. Can the Japanese keyword hack infect my site through plugins?

Yes, outdated or vulnerable plugins are the most common entry point for the WordPress Japanese keyword hack.

Regularly updating or removing unused plugins significantly reduces your risk of infection.

3. Will changing my passwords help in fixing the Japanese keyword hack?

Password changes are an essential but insufficient step in fixing the Japanese keyword hack.

While new passwords prevent unauthorized access through legitimate channels, most infections persist through backdoors and modified files that operate independently of your authentication system.

Complete removal requires file cleaning, database scanning, and backdoor elimination alongside credential updates.

4. How quickly do search engines recover after removing the hack?

Recovery time varies based on several factors:

The median recovery time for proper removal is approximately 18 days before search visibility returns to pre-hack levels.

5. Can I clean the Japanese keyword hack without taking my site offline?

While technically possible, cleaning without downtime significantly increases risk.

During the cleaning process, visitors may encounter malicious redirects or exposed malware.

Additionally, search engines might crawl your site mid-cleanup, potentially indexing partially cleaned pages.

For professional results when fixing the Japanese keyword hack, implementing brief scheduled maintenance (typically 2-4 hours) is strongly recommended.

6. How can I be sure the Japanese keyword hack is completely removed?

Complete removal verification requires multiple approaches:

1. Clean file comparison with a fresh WordPress installation.
2. Database scanning with multiple security tools.
3. User agent spoofing to test search engine-specific redirects.
4. Monitoring server logs for unusual access patterns.
5. Observing site behavior through multiple devices and locations.