How to Clean Up Your Website After an eval(base64_decode) Virus Infection?

How to Get Rid of eval-base64_decode Virus Files

Problem:

Your website has been infected with a virus that inserts malicious PHP code into PHP files, beginning with eval(base64_decode('. This code can compromise your site and allow attackers to execute arbitrary commands.

Security Hole:

The virus typically exploits vulnerabilities in web applications or plugins that allow attackers to upload or execute malicious code.

PHP Code Analysis:

The PHP code uses several techniques:

• Base64 decoding to obfuscate the malicious code.
• Disables error reporting with error_reporting(0);.
• Checks for specific user agents and IP addresses to bypass security measures.
• Inserts an invisible iframe that retrieves and executes malicious code.

Iframe Code:

The iframe attempts to load a hidden server from http://lzqqarkl.co.cc/QQkFBwQGDQMGBwYAEkcJBQcEAAcDAAMBBw==. This server may host additional malicious code or redirect to phishing sites.

Steps to Clean Your Site:

1. Shutdown the Site:

• Temporarily block access to your site using your web server's configuration.

2. Download All Files:

• Create a backup of your entire site.

3. Install File Comparison Utility:

• Use a utility like WinMerge or DiffMerge to compare your files to the backup.

4. Compare Files:

• Identify and restore any files that have been modified or deleted.
• Overwrite any files with malicious code with their clean counterparts.

5. Review Security Measures:

• Update passwords, remove unused plugins, and review the security settings of your applications and server.

6. Check Site Functionality:

• Verify that your site is working correctly after cleaning.

7. Implement Automated Detection:

• Use tools like Tripwire or log监控器 to identify file changes.

8. Schedule Backups:

• Regularly back up your site and retain multiple versions.

9. Monitor Your Site:

• Keep an eye on your logs for suspicious activity or access attempts.

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