Popup warnings of missing fonts, specifically the Hoeflertext font, are being used to infect users with malware. The Hoeflertext warnings appear as popups when users visit compromised websites using the Chrome or Firefox browsers. The warnings flash up on screen with the website in the background displaying jumbled or unreadable text.

Hoeflertext is a legitimate font released by Apple in 1991, although popup warnings that the font is missing are likely to be a scam to fool users into downloading Locky Ransomware or other malware.

Visitors to the malicious websites are informed that Hoeflertext was not found, which prevents the website from being displayed. The popup contains an option to “update” the browser with a new font pack, which will allow the website content to be displayed.

Clicking on the update button will not install a font pack, instead it will launch a download of a JavaScript script file – Win.JSFontlib09.js. If that file is saved and opened, it will download Locky ransomware onto the user’s device.

This is not the first time the Hoeflertext font scam has been used. NeoSmart Technologies discovered the scam in February this year, although recently both Palo Alto Networks and SANS Internet Storm Center have both report it is being used in a new campaign.

Another version of the campaign is being used to deliver the NetSupport Manager remote access tool (RAT). In this case, the file downloaded is called Font_Chrome.exe, which will install the RAT if it is run. The researchers suggest the RAT is being favored as it offers the attackers a much wider range of capabilities than ransomware. The RAT is commercially available and has been used in several malware campaigns in the past, including last year’s campaign using hacked Steam accounts.

The RAT, once installed, gives the attackers access to the infected computer allowing them to search for and steal sensitive information and download other malware.

The actors behind this campaign have been using spam email to direct users to the malicious websites where the popups are displayed. The SANS Internet Storm Center says one campaign has been identified using emails that appear to have been sent via Dropbox, asking the user to verify their email address to complete the sign-up process.

Clicking on the ‘verify your email’ box will direct the user to a malicious website displaying fake Dropbox pages where the popups appear. Internet Explorer users do not have the popups displayed, instead they are presented with a fake anti-virus alerts linked to a tech support scam.

The latest campaign shows why it is so important for businesses to use an advanced spam filtering solution to block malicious messages. A web filtering solution is also beneficial to prevent end users from visiting malicious websites in case the messages are delivered and opened. Along with security awareness training for employees to alert them to the risks of email and web-based attacks such as this, businesses can protect themselves from attack.