Executable file extensions

The list at the right is a partial list of file types that should be considered suspicious when received in email and should not be opened unless you requested or expected the attachment.  The three letters in the first column are file extensions, the three letters that follow the dot in a file name (i.e. document.doc) All of these file types are executable, meaning that when opened, they have the ability to run computer code just as if they were an application.  Word (.doc) and Excel (.xls) files may contain a macro virus, which can run code as well.   The most dangerous and common are shown in red.

(Courtesy of About.com)

ADE

 Microsoft Access Project Extension

ADP

 Microsoft Access Project

BAS

 Visual Basic Class Module

BAT

 Batch File

CHM

 Compiled HTML Help File

CMD

 Windows NT Command Script

COM

 MS - DOS Application

CPL

 Control Panel Extension

CRT

 Security Certificate

DLL

 Dynamic Link Library

DO*

 Word Documents and Templates

EXE

 Application

HLP

 Windows Help File

HTA

 HTML Applications

INF

 Setup Information File

INS

 Internet Communication Settings

ISP

 Internet Communication Settings

JS

 JScript File

JSE

 JScript Encoded Script File

LNK

 Shortcut

MDB

 Microsoft Access Application

MDE

 Microsoft Access MDE Database

MSC

 Microsoft Common Console Document

MSI

 Windows Installer Package

MSP

 Windows Installer Patch

MST

 Visual Test Source File

OCX

 ActiveX Objects

PCD

 Photo CD Image

PIF

 Shortcut to MS-DOS Program

POT

 PowerPoint Templates

PPT

 PowerPoint Files

REG

 Registration Entries

SCR

 Screen Saver

SCT

 Windows Script Component

SHB

 Document Shortcut File

SHS

 Shell Scrap Object

SYS

 System Config/Driver

URL

 Web Address (Uniform Resource Locator)

VB

 VBScript File

VBE

 VBScript Encoded Script File

VBS

 VBScript Script File

WSC

 Windows Script Component

WSF

 Windows Script File

WSH

 Windows Scripting Host Settings File

XL*

 Excel Files and Templates