Some days ago I wrote in this post how you can “fight” against spam, with some tips which you can do to protect yourself against spam. One of those tips was to filter mails containing executable file extensions in attachments, but which executable file extensions do you have to filter out??

Invisible Files
Some file extensions are by default suppressed from displaying in Windows Explorer and other programs. This allows virus writers and malicious code to distribute executable files disguised as something non-executable. For example, a *.exe file might appear to be a text file.

Executable File Extensions
The following is a list of file types that should be considered suspicious when received as attachment in mails. These files and should not be opened unless you really know what they contain. Many viruses and malicious software distributes by sending its content as an attatchment with such an extension.

• *.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 Internet Shortcut (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