---
title: What are the Dangerous File Attachments?
description: "**What are the Dangerous File Attachments?** The following is a list of file attachments that may be blocked by the Mail Scanner service (the attachments are removed from emails before delivery to you)   ![ما هي مرفقات الملفات الخطيرة؟](https://www.hyyat.com/wp-content/uploads/2022/06/371154Image1-1180x677_d-300x172.jpg) **These…"
url: "https://www.hyyat.com/en/knowledgebase/what-are-the-dangerous-file-attachments/"
updated: "2026-10-21"
category: "E-mail / spam"
tags:
  - mail
  - spam
---

# What are the Dangerous File Attachments?

**What are the Dangerous File Attachments?**

The following is a list of file attachments that may be blocked by the Mail Scanner service (the attachments are removed from emails before delivery to you)

 

![ما هي مرفقات الملفات الخطيرة؟](https://www.hyyat.com/wp-content/uploads/2022/06/371154Image1-1180x677_d-300x172.jpg)

**These extensions are known to be dangerous in almost all cases.**

- - .reg Possible Windows registry attack

 

- - .chm Possible compiled Help file-based virus

 

- - .cnf Possible SpeedDial attack

 

- - .hta Possible Microsoft HTML archive attack

 

- - .ins Possible Microsoft Internet Comm. Settings attack

 

- - .jse_ Possible Microsoft JScript attack

 

- - .lnk Possible Eudora *.lnk security hole attack

 

- - .ma_ Possible Microsoft Access Shortcut attack

 

- - .pif Possible MS-Dos program shortcut attack

 

- - .scf Possible Windows Explorer Command attack

 

- - .sct Possible Microsoft Windows Script Component attack

 

- - .shb Possible document shortcut attack

 

- - .shs Possible Shell Scrap Object attack

 

- - .vbe or .vbs Possible Microsoft Visual Basic script attack

 

- - .wsc .wsf .wsh Possible Microsoft Windows Script Host attack

 

- - .xnk Possible Microsoft Exchange Shortcut attack

**These 2 are Very often used by viruses**

- - .com Windows/DOS Executable

 

- - .exe Windows/DOS Executable

**These are very dangerous and have been used to hide viruses**

- - .scr Possible virus hidden in a screensaver

 

- - .bat Possible malicious batch file script

 

- - .cmd Possible malicious batch file script

 

- - .cpl Possible malicious control panel item

 

- - .mhtml Possible Eudora meta-refresh attack

**Deny filenames ending with CLSID's**

- {[a-hA-H0-9-]{25,}\} Filename trying to hide its real extension
   Examples:
   A977FF0C-8757-4E76-8533-482F91946233
   000209FF-0000-0000-C000-000000000046

**Deny filenames with lots of contiguous white space in them.**

- Filename contains lots of white space **Deny all other double file extensions. This catches any hidden filenames.**
- Found possible filename hiding
   Examples:
   .txt.pif
   .doc.pif
   .doc.com
   .txt.exe

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