How to Find a Backdoor in a Hacked WordPress Site and Fix It

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Has your WordPress website been hacked?

Hackers will often install a backdoor to make sure they can get back in even after you secure your website. Unless you can remove that backdoor, there’s no stopping them.

In this article, we’ll show you how to find a backdoor in a hacked WordPress site and fix it.

But what if your site has already been hacked?

And don’t forget to close the backdoor.

A smart hacker knows that you’ll eventually clean up your website. The first thing they might do is install a backdoor, so they can sneak back in after you secure the front door to your WordPress website.

A backdoor is code added to a website that allows a hacker to access the server while remaining undetected, and bypassing the normal login. It allows a hacker to regain access even after you find and remove the exploited plugin or vulnerability to your website.

Backdoors often survive WordPress upgrades. That means your site will remain vulnerable until you find and fix every backdoor.

How Do Backdoors Work?

Some backdoors are simply hidden admin usernames. They let the hacker log in as normal by typing a username and password. Because the username is hidden, you’re not even aware that someone else has access to your website.

More complex backdoors can allow the hacker to execute PHP code. They manually send the code to your website using their web browser.

Some hackers will leave more than one backdoor file. After they upload one, they will add another to ensure their access.

Where Are Backdoors Hidden?

In every case we’ve found, the backdoor was disguised to look like a WordPress file. The code for backdoors on a WordPress site are most commonly stored in the following locations:

Examples of Backdoors We’ve Found

Here are some examples of where hackers have uploaded backdoors. In one site we cleaned up, the backdoor was in the wp-includes folder. The file was called wp-user.php, which looks innocent enough, but that file doesn’t actually exist in a normal WordPress installation.

In another instance, we found a PHP file named hello.php in the uploads folder. It was disguised as the Hello Dolly plugin. What’s strange is that the hacker put it in the uploads folder instead of the plugins folder.

We’ve also found backdoors that don’t use the .php file extension. One example was a file named wp-content.old.tmp, and we’ve also found backdoors in files with a .zip extension.

As you can see, hackers can take very creative approaches when hiding a backdoor.

In most cases, the files were encoded with Base64 code that can perform all sorts of operations. For example, they can add spam links, add additional pages, redirect the main site to spammy pages, and more.

With that being said, let’s take a look at how to find a backdoor in a hacked WordPress site and fix it.

Now you know what a backdoor is and where it might be hidden. The difficult part is finding it! After that, cleaning it up is as easy as deleting the file or code.

1. Scan for Potentially Malicious Code

2. Delete Your Plugins Folder

Searching through your plugin folders looking for suspicious files and code is time consuming. And because hackers are so sneaky, there’s no guarantee you will find a backdoor.

You will need to use the software to navigate to your website’s wp-content folder. Once there, you should right click on the plugins folder and select ‘Delete’.

3. Delete Your Themes Folder

In the same way, instead of spending time searching for a backdoor among your theme files, it’s better just to delete them.

After you delete your plugin folder, simply highlight the themes folder and delete it in the same way.

You don’t know whether there was a backdoor in that folder, but if there was, it’s gone now. You just saved time and you eliminated an extra point of attack.

Now you can reinstall any themes that you need.

4. Search the Uploads Folder for PHP Files

Next, you should take a look through the uploads folder and make sure that there are no PHP files inside.

There is no good reason for a PHP file to be in this folder because it’s designed to store media files such as images. If you find a PHP file there, then it should be deleted.

Like the plugins and themes folders, you’ll find the uploads folder in the wp-content folder. Inside the folder you will find multiple folders for each year and month you have uploaded files. You will need to check each folder for PHP files.

Some FTP clients offer tools that will search the folder recursively. For example, if you use FileZilla, then you can right click the folder and select ‘Add files to queue’. Any files found in any subdirectories of the folder will be added to the queue in the bottom pane.

You can now scroll through the list looking for files with the .php extension.

Alternatively, advanced users who are familiar with SSH can write the following command:

5. Delete the .htaccess File

Using an FTP client or file manager, simply delete the file from your website’s root directory, and it will be recreated automatically.

If for some reason it isn’t recreated, then you should go to Settings » Permalinks in your WordPress admin panel. Clicking the ‘Save Changes’ button will save a new .htaccess file.

6. Check the wp-config.php File

The file is found in your website’s root folder. You can view the file’s contents by selecting the Open or Edit options in your FTP client.

Now you should look at the contents of the file carefully to see if there is anything that looks out of place. It might be helpful to compare the file with the default wp-config-sample.php file which is located in the same folder.

You should delete any code that you’re certain doesn’t belong.

7. Restore a Website Backup

If you have been making regular backups of your website and are still concerned that your website isn’t completely clean, then restoring a backup is a good solution.

You will need to completely delete your website and then restore a backup that was taken before your website was hacked. This isn’t an option for everyone, but it will leave you 100% confident that your site is safe.

Now that you’ve cleaned up your website, it’s time to improve your site’s security to prevent hacks in the future. It doesn’t pay to be cheap or apathetic when it comes to website security.

1. Regularly Backup Your Website

If you don’t already make regular backups of your website, then today is the day to start.

2. Install a Security Plugin

We recommend Sucuri because they’re good at what they do. Major publications like CNN, USA Today, PC World, TechCrunch, The Next Web, and others agree. Plus, we rely on it ourselves to keep WPBeginner secure.

3. Make WordPress Login More Secure

4. Protect Your WordPress Admin Area

5. Disable Theme and Plugin Editors

Did you know that WordPress comes with a built-in theme and plugin editor? This plain text editor allows you to edit your theme and plugin files directly from the WordPress dashboard.

While this is helpful, it can lead potential security issues. For example, if a hacker breaks into your WordPress admin area, then they can use the built-in editor to gain access to all your WordPress data.

6. Disable PHP Execution in Certain WordPress Folders

For example, WordPress never needs to run code stored in your uploads folder. If you disable PHP execution for that folder, then a hacker won’t be able to run a backdoor even if they successfully uploaded one there.

7. Keep Your Website Up to Date

Every new version of WordPress is safer than the previous one. Whenever a security vulnerability is reported, the core WordPress team works diligently to release an update that fixes the issue.

This means that if you are not keeping WordPress up to date, then you are using software with known security vulnerabilities. Hackers can search for websites running the older version and use the vulnerabilty to gain access.

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