Many PHP-based web shells are still making the rounds, and while many of them are based on old code, mutations, customizations and updates abound. They are so common, that new variants and modified versions are often seen at the rate of about 10 a day in our TigerTrax Threat Intelligence systems and honeypots.

Variants exist for a wide variety of platforms and human languages, many with some very nasty features and even some cool ASCII art. There are many variants for attackers to choose from for just about any of the popular PHP-based content management platforms. From WordPress to Joomla and beyond to the far less common apps, there are easily used exploits and shell kits widely available.

If you run a PHP-based site or server, it’s a good idea to keep an eye on the file system changes and watch closely for new files being uploaded or added. Pay particular attention to those using the “base64_decode” function, since it is so common among these tools.

Thanks for reading, and until next time, stay safe out there!