As a WordPress site user – or any other online platform – we keep hearing about backdoors and how they are dangerous if left unsupervised as hackers can exploit these to gain full access to your site. So, what’s the deal?
What are backdoors?
Backdoor, or malicious backdoor, is code that lets hackers gain illegitimate and unrestricted access to your site – this includes all the content and files under the hosting account, the core files that maintain the functioning of the site, and sensitive data of customers.
Often looking important in the form of PHP code or some other ambiguous form that doesn’t incite much attention from the site owner, it is cleverly hidden and obscured so as to strike at any time. Any valid file can contain just a single line of malicious code that doesn’t look questionable at the first glance, or it could be a standalone file.
It functions as an entry point for other malware infections and allows the attacker to further place malicious code anywhere on the site, making it difficult to clean up and potentially compromising customer security or inviting data breach.
How do you know if you’re a victim?
As mentioned above, hidden and obfuscated code is intentionally difficult to find, so it might be a long time before you’ve concrete proof that your site is compromised. If there are more than one backdoors, they need not be in the same pattern or have the same purpose.
Most times, it is equally possible that backdoors are accidental, where unsecured maintenance scripts are left behind after a period of site maintenance that can lead to wordpress being hacked.
Site owners may keep in mind that any episodes of malware or hacking are possible through backdoor files or code injections which pave the way for the attacker to enter the site, so that’s one time you can be sure of its presence.
Finding and Removing Backdoors
Removal of backdoors is an equally difficult task, requiring in-depth analysis of the site code. Most often, they are found in PHP files on the webserver, or inserted into extensions, themes, or plugins, or even as standalone files. If you have publicly accessible directories on your server, then this is possibly a source of backdoors as attackers can easily place them here.
- Backup – All removal procedures start with a backup of the site for restoration purposes after cleaning the backdoors. Include all site files and databases, and make sure to review the raw HTTP access log files since this is where backdoor usage is done after a post HTTP request to the file.
- Administrative accounts – User/Admin accounts that are compromised also allow the attacker to enter the site and use facilities like the core theme editor to place a backdoor in the theme’s 404 files. This means that every time someone tries to access your site, a 404 error page is generated and a convenient backdoor appears which can be used by anyone who knows of its presence.
- Find out the code – Therefore, removing the backdoor means finding out the incriminating code which has allowed the hacker unauthorized access and understanding how it operates before precisely removing it.
- Backdoors in rogue files – Some rogue file backdoors, or backdoors found in files that are not part of the core plugin, themes, or the CMS platform, appear with innocent-looking names like xml.php or plugin.php, etc. These can be placed anywhere on the site, so analyzing each file and not just the extra files added is very important.
- Backdoor plugins and themes – A compromised administrative account can also lead the hacker to use the plugin or theme upload abilities to place backdoors strategically.
This addition may not appear on the plugin administration page. Such compromised plugins are necessarily hidden from view and are only visible on the network through the file manager or the FTP. You can expect useful names for these as well, such as WordPress Support, WP-Base-SEO, etc. One backdoor can lead to the addition of many more, especially those that influence the functionality of core files.
Always remove those files or extensions that you don’t recognize and review the existing ones to check if they are still required, from trusted third-party providers or the official repository, and if they’re updated to the most current versions.
Backdoors are mostly the beginning to the end – they point towards the presence of other malware on the site such as spam pages, links, malicious redirects, etc. An important piece of information about backdoors is their origin – since the attacker has exploited some pre-existing security vulnerability to place it there.
Multiple backdoors is not a rare occurrence, and one can expect both similar and different versions as well, so a review of the entire site is crucial to maintain the site and your customers.
If all of this information is overwhelming, or you have specific requirements, don’t forget to contact professionals like Astra Security for your backdoor cleaning needs!