09/16/2026
Email attachments are a common way attackers deliver malware because they can disguise harmful files as something familiar, like an invoice, document, or shared file.
The important thing to know is that opening a file can give malware a way into your system. Some file types can actually run programs or commands on your computer as soon as you open them.
Here are a few worth recognizing:
⚠️ .exe, .scr, .msi
These are program files. Opening one can install or run software on your computer. A normal invoice, quote, or document usually won’t be sent this way.
⚠️ .js, .vbs, .bat, .cmd, .ps1
These are script files that can run commands on your computer. Unless you were specifically expecting one, treat it with caution.
⚠️ Office files asking you to “enable macros” or “enable content”
Macros can run code inside a document. If a file is asking you to turn them on before you can view it, stop and verify the file first.
⚠️ .iso and .img files
These disk image files aren’t common in everyday business email, but attackers can use them to hide malicious files or get around security filters.
If you weren’t expecting an attachment, verify it before opening it. Even if it came from someone you know, their email account could be compromised.
At CisCom, we help give your team the tools, protection, and support they need to work confidently and make smart security decisions. Because good cybersecurity isn’t just about blocking threats. It’s about setting your people up to succeed.