A central promise of our Managed Spam Filter Services is to protect our customers from malicious mails. Especially the automatic detection of spam and malicious software has rapidly gained importance in recent months – Locky, Tesla, Petya and co. send their regards! The Content Filter is an additional, customizable protection. Customers can use it to independently control the handling of attachments contained in incoming and outgoing emails. The maximum file size for attachments can thus be set – although the Content Filter’s ability to detect certain types of file extensions is much more important. This allows administrators to define specific file extensions, thus preventing the delivery of an email with the relevant attachment.  

The content filter can be quickly activated and customized in the control panel

Specifically, this means: If an IT manager wants to prevent their email users from receiving attachments with the .exe extension, they need only enable the Content Filter (if not already activated) and enter .exe into the open field. As a special service and for ease of use, we have set up several group extensions to provide improved protection in all the default settings: .executable, .mediafile, .xlsmacro and .docmacro. If, for example, “.executable” is specified, the Content Filter automatically blocks 58 extensions of executable files. This group extension is continuously maintained and kept up to date in order to always ensure the highest possible protection. The extension .mediafile, for example, can be used to filter out files with the extensions .wav, .mp3, .mid. mpg and several others. The two other collective terms are specifically designed to retain macros in Excel and Word files, which often transmit links to blackmailer viruses. The Content Filter can incidentally be configured for the entire domain as well as for specific groups within a domain.   If not already enabled, we thus urgently advise all customers and partners of Hornetsecurity to activate the Content Filter free of charge and add the file extension “.executable” to their list of files to be blocked. They can ramp up their protection another notch by doing so. The screenshot shows how this is done.   Note: This blog post was first published in April 2015 and has now been updated and adapted to the new ransomware threats.