The presence of a file named bak.php in your WordPress installation can raise a few possibilities, depending on how it was created and what its purpose is. The .bak extension or naming convention typically signifies a “backup” file, but the fact that this file has a .php extension indicates that it’s a PHP script, which could have been saved or generated as a backup copy of an existing file. Here are six possible explanations for why you have a file called bak.php:
1. Backup of a PHP File
The most straightforward reason for the existence of bak.php is that it could be a backup copy of a critical PHP file on your website. Developers or site administrators often create backup files before making changes to core theme or plugin files. By renaming a file with the .bak suffix, the original file remains intact while giving developers or administrators the flexibility to revert any changes if something goes wrong. In this case, bak.php may contain older versions of PHP code from your site before a recent update or modification.
2. Manually Created Backup by Developer
If you or someone else working on the website has been modifying PHP files—perhaps within the theme or a plugin—it is possible that the file was manually created as a backup for safety reasons. Developers often duplicate and rename files to file.bak.php or bak.php when they’re about to make significant changes, ensuring that there’s a copy of the original code in case the new modifications cause problems. This allows for easy restoration of the previous version by simply renaming the backup file to its original filename.
3. Generated by a Backup Plugin or Tool
Many WordPress backup plugins or hosting backup systems automatically generate and store backup files of important PHP scripts and other site components. In some cases, these automated tools use naming conventions like bak.php to signal that a particular file is a backup. If you’re using a backup plugin, it’s possible that bak.php was created as part of a restoration process or during an automated backup. However, backup plugins generally store files in a more organized way (like in a /backups/ directory), so it would be unusual for the file to appear in the root or theme folder unless the backup process was misconfigured.
4. Malicious File Created by an Attacker
While bak.php may be a legitimate backup, there’s also a possibility that it could be a malicious file uploaded by an attacker. Hackers often upload files with names that seem harmless or generic, like bak.php, to hide malicious scripts or backdoors in the WordPress environment. These files can contain code designed to compromise the site’s security, allowing unauthorized access, data exfiltration, or execution of commands. To ensure that bak.php is not malicious, it’s crucial to inspect its contents for any suspicious or obfuscated code. If the file includes unusual functions like eval(), base64_decode(), or references to external malicious URLs, it could indicate that the file was uploaded as part of a hack.
5. Leftover File After a Migration or Update
If your WordPress site was recently migrated from one server to another or updated manually, bak.php might be a leftover file from that process. During migrations or updates, files are often duplicated or renamed for safety. In this case, bak.php could have been a temporary backup that wasn’t removed after the migration or update was completed. It’s not uncommon for developers to leave behind old backup files unintentionally, especially if they’re in a rush or dealing with large numbers of files during the transfer process.
6. Conclusion and Next Steps
In conclusion, bak.php is likely a backup file either created manually by a developer, generated by a backup tool, or left behind from an update or migration. However, there’s also the risk that it could be a malicious file placed on your site by an attacker. To ensure the safety and functionality of your website, it’s important to verify the purpose of bak.phpby examining its contents. If it’s a legitimate backup, you can safely delete it or move it to a more secure location. If you find any suspicious code or have no reason to believe it was created intentionally, it’s recommended to remove the file and scan your WordPress installation for other potential security issues. Regular monitoring, security plugins, and backups can help prevent the risk of malicious files in the future.