Security researchers discovered a hidden HTTP directory that is allowing threat actors to install Shade ransomware on WordPress and Joomla websites.

The campaign has compromised at least 500 online properties and is taking aim at thousands more, Zscaler warned. Victims of the attack were targeted via phishing emails that contained a ZIP file with JavaScript, which in turn downloaded and ran Shade ransomware. The directory is one that website owners often use to prove to certificate authorities that they have rights to a particular domain.

Who’s at Risk of a Web Phishing Attack?

WordPress and Joomla are among the most popular content management systems (CMSs). The current Shade ransomware threat is most likely to affect sites running server-side software and outdated themes or plugins, the researchers said. Those vulnerable include websites running WordPress versions 4.8.9 to 5.1.1.

Using the directory means those behind the attacks can effectively hide the files containing Shade ransomware — otherwise known as Troldesh — from WordPress and Joomla admins, Zscaler added. Once the payload has been executed, threat actors are able to change the wallpaper of a victim’s machine to show a ransom note written in Russian and English.

The attackers have also been careful to use phishing pages that resemble some of the most common productivity tools, including Microsoft OneDrive, DropBox and Gmail. However, there were other pages designed to imitate firms such as Bank of America and DHL, according to screenshots the researchers captured. This means threat actors might easily be able to steal usernames, passwords and other confidential information.

Stopping the Spread of Shade Ransomware

While the source of the current Shade ransomware campaign against WordPress and Joomla users is unknown, security teams should act quickly to limit the potential for similar phishing attacks.

A good incident prevention plan not only includes keeping up to date on current website themes and plugins, but also, as IBM experts recommend, using identity verification and multifactor authentication tools that can spot threats that might be hidden to a website admin.