Email remains one of the most common ways cybercriminals attempt to gain access to business systems. While many people know to be cautious of suspicious links, dangerous file attachments can be just as risky. Understanding which file types require extra scrutiny can help protect your business from malware, ransomware, and data breaches.

One of the highest-risk attachment types is executable files, including extensions such as .exe, .bat, .cmd, and .msi. These files are actual programs that run on your computer and can execute virtually any code. Unless you are expecting them from a trusted source, they should be treated with extreme caution.

Another common threat comes from macro-enabled Microsoft Office documents, including .docm, .xlsm, and .pptm files. Unlike standard Office documents, these files contain embedded code that can run automatically when macros are enabled. Cybercriminals often use them to install malware or steal information.

Businesses should also be wary of script and web files, such as .js, .vbs, .html, and .hta files. These file types can execute code through your browser or operating system and are frequently used in phishing and malware campaigns.

Finally, archive files like .zip, .rar, and .7z can present a hidden risk. While archives are commonly used for legitimate file sharing, they can conceal malicious content and make it more difficult to identify dangerous files. Password-protected archives sent unexpectedly should raise particular concern.

Before opening any attachment, verify the sender’s email address, confirm you were expecting the file, and check the file extension carefully. Be especially cautious of double extensions such as “invoice.pdf.exe,” which are designed to disguise malicious files as legitimate documents.

Cybersecurity often comes down to awareness. Taking a few extra seconds to inspect an attachment could prevent a costly security incident.

Get in touch to see how we can help train your team on what to look out for.