Potentially "Unsafe" Filetypes
** Updated 6/26/2000
The following list contains the types of files that can contain programs, and which can, if opened or run, make changes to your disk drive's contents. Because of this ability, these files are potentially "unsafe", meaning they could do harm. Open these files with caution. Always know the source of the file, and its purpose.
For more information, read:
- Karen's June 26, 2000 Power Tools newsletter.
- Karen's June 19, 2000 Power Tools newsletter.
- Karen's June 12, 2000 Power Tools newsletter.
First, here's Microsoft's list of potentially "unsafe" files. These are the files that cannot be received as email attachments, after you install the "Security Update" for Outlook 2000 and Outlook 98. These types of files, and others we'll see in a moment, are highlighted by Karen's Directory Printer.
Updated 6/26/2000
This "classic" list is not a complete accounting of the modern filetypes that might feature unsafe automation.
Extension | Description |
.ade | Microsoft Access project extension |
.adp | Microsoft Access project |
.bas | Microsoft Visual Basic class module |
.bat | Batch file |
.chm | Compiled HTML Help file |
.cmd | Microsoft Windows NT Command script |
.com | Microsoft MS-DOS program |
.cpl | Control Panel extension |
.crt | Security certificate |
.exe | Program |
.hlp | Help file |
.hta | HTML program |
.inf | Setup Information |
.ins | Internet Naming Service |
.isp | Internet Communication settings |
.js | JScript file |
.jse | Jscript Encoded Script file |
.lnk | Shortcut |
.mdb | Microsoft Access program |
.mde | Microsoft Access MDE database |
.msc | Microsoft Common Console document |
.msi | Microsoft Windows Installer package |
.msp | Microsoft Windows Installer patch |
.mst | Microsoft Visual Test source files |
.pcd | Photo CD image, Microsoft Visual compiled script |
.pif | Shortcut to MS-DOS program |
.reg | Windows Registry entries |
.scr | Screen saver |
.sct | Windows Script Component |
.shb | Shell Scrap object |
.shs | Shell Scrap object |
.url | Internet shortcut |
.vb | VBScript file |
.vbe | VBScript Encoded script file |
.vbs | VBScript file |
.wsc | Windows Script Component |
.wsf | Windows Script file |
.wsh | Windows Script Host Settings file |
Microsoft's latest list can be found on their web site at http://support.microsoft.com/support/kb/articles/Q262/6/31.html.
In addition, the newest Directory Printer highlights these additional types of executable files:
Extension | Description |
.286 | A device driver written for Windows 2.0 and 3.x real mode |
.386 | A device driver written for Windows 3.x |
.vxd | Virtual device Driver, a program that emulates hardware |
.dll | A Dynamic Link Library, contains reusable small routines |
.ocx | An ActiveX control, a small program used by other programs. |
.vbx | An early, 16-bit predecessor of ActiveX controls |
.drv | A Windows or DOS device driver |
.ovl | A type of DOS program file, similar to Windows .DLL files |
.scf | Windows Explorer Command |
.sys | An extension to DOS, loaded when the computer boots |
.qtx | A program that adds features to Apple's QuickTime program |
.fot | Older TrueType font files. These are actually programs |
.rom | A copy of a program normally stored in ROM (Read-Only Memory) |
.class | Java Applet (small program written in Java programming language) |
.job | A list of programs to be run at a specific time |
Directory Printer also highlights several types of files that can contain scripts or other types of small programs. Some scripts can do harm directly, while others can call DLLs and other types of executable files, to do damage.
Extension | Description |
.htm | Web page, which may contain scripts |
.html | Same as .htm |
.htt | HyperText Template, which can contain same information as .htm |
.doc | Microsoft Word document |
.wll | Microsoft Word add-in |
.dot | Microsoft Word template |
.wiz | Microsoft Word Wizard |
.xls | Microsoft Excel spreadsheet or worksheet |
.xla | Microsoft Excel add-in |
.xll | Microsoft Excel add-in |
.xlt | Microsoft Excel template |
.mdt | Microsoft Access add-in |
.mdz | Microsoft Access database template/wizard |
.pot | Microsoft PowerPoint template |
.ppa | Microsoft PowerPoint add-in |
.wpt | WordPerfect template |
.wpm | WordPerfect macro |
.mht | Microsoft Internet Explorer single-file HTML archive |
Change History
- Thanks to reader Bob Dietz for the addition of the .wll and .xll file types.
- Thanks to reader Tim McGowan for the addition of the .wpm and .wpt file types.
- Thanks to reader Dan DeYoung for the addition of the .mht file type.
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