We are currently getting swamped with hacked Joomla websites with a malicious security.php file in their root directory (e.g. at the same level of the index.php file). The name of that file is extremely misleading because it implies security, while, in reality, it is the complete opposite. In fact, Joomla websites should not contain a file carrying this name anywhere (not in the root directory, not even in any subdirectory).
Ever since August 20th, 2016 (it was when we saw the first occurrence of the security.php file), we are seeing more and more of these malicious files on Joomla websites.
So, how is this file uploaded onto the Joomla website?
In most cases, the file was uploaded using an exploit on the Joomla website, and that exploit is typically a vulnerable extension. We know that because the absolute majority of Joomla websites infected with that file are running the latest Joomla version (3.6.2 at the time of writing this article), which is known to be secure. In some cases, the file gets uploaded because of a vulnerability on the LAMP server, but again, the absolute majority of the time the culprit is an outdated extension.
So, what does this file do?
The security.php file is a main backdoor file, that is used to control the Joomla website (even when all the other exploits [vulnerable extensions, outdated Joomla website, vulnerable server] are closed) by allowing the attacker to execute remote commands comfortably. The fact that it has this trustworthy name lets it go unnoticed by many Joomla administrators, who are misled into thinking that this file is actually about security, and deleting it might compromise the security of their websites. In fact, we had several people emailing us about this file as they have never seen it before (almost all of them were convinced that it was part of Joomla 3.6.2 security).
So, what can someone do to protect his Joomla website from that file?
The best way to protect a Joomla website from the malicious security.php is to prevent the upload in the first place by closing all the possible exploits, which consists of: updating the Joomla website to the latest secure version, removing unnecessary and vulnerable extensions, updating all the extensions, and ensuring that the environment is secure (e.g. Linux, Apache, MySQL, and PHP do not have any vulnerabilities).
There is also a fallback protection method, which consists of only allowing the index.php to be access from the outside world as described here.
If you ever see a security.php under the root directory of your Joomla website (or anywhere on your Joomla website, for that matter), then you should resign to the fact that your website is hacked and you should proceed accordingly (you should clean it up and secure it). If you need help with unhacking and securing your Joomla website, then look no further: we are the Joomla security experts! Just contact us and we’ll ensure that your website has stellar security in no time and for very little money!