Hundreds of websites have been infected with malware that masquerades as legitimate ionCube-encoded files, SiteLock warns.
The malicious files were initially discovered in core directories of a WordPress site, featuring naming patterns usually associated with malware, namely “diff98.php” and “wrgcduzk.php.” Because the obfuscated files appear as if they had been encoded with ionCube, the researchers named the threat ionCube malware.
ionCube is an old and powerful PHP obfuscation technology that can be used to scramble text-based PHP files to hide the intellectual property. Due to licensing costs, ionCube isn’t usually used for malicious purposes.
Malicious attackers, however, found a way to pack their malware in a manner that resembles that of ionCube-encoded files, and started targeting various websites. Although the infection was initially spotted on a WordPress site, SiteLock’s researchers discovered that Joomla and CodeIgniter sites have been infected as well.
According to SiteLock, the malware is likely to run on any web server running PHP, and could hide in plain sight by using filenames such as “inc.php” and “menu.php.” Overall, the researchers discovered over 7,000 infected files and say that over 700 sites were compromised.
Once decoded, the fake ionCube files turn into the malware itself, which still contains some obfuscation, along with some sort of access control, researchers discovered.
“While there’s still some degree of obfuscation, the presence of the $_POST and $_COOKIE superglobals and the eval request at the end of the file reveal its true purpose: to accept and execute remotely supplied code. It looks like the remote code supplied to this file is further obfuscated and there may be some sort of access control implemented, judging by the GUID-formatted string present,” SiteLock says.
Site administrators who haven’t specifically and intentionally installed ionCube-encoded files but do find such files on their servers were likely infected. If an infection is detected, the scanning of the entire site is recommended, to completely eliminate the threat.
According to SiteLock, differentiating between the fake and legitimate files can be very difficult as well, given the large number of malware variations out there. The researchers say it is common to see up to 100 slightly different variants of the malware on a single site.