The most known file type that is invisible is .SHS, since the "Life Stages" virus used this "feature" to camouflage a virus in what looked like an innocent .TXT ascii file. But the most common invisible file type is used by patically everybody, and that is the .LNK, which are the shortcuts you use on your desktop or menus to open up applications and files. We use to take these shortcuts as an oblect of the operationg system, but in fact they are only small files, with a hidden .LNK extension appended to it.
So, back to .SHS, it stands for Shell Scrap. It's an old dinausor from Windows 3.1 that have been mostly unkown until only a couple of years ago. It is used for OLE (Object Linking and Embedding), and using a Shell Scrap, you can just include any file you want, even an executable, in a Word document, for example, and the system will open it for you. The .SHS file will bear an icon ressembling somewhat the one of Notepad, but still slightly different (the bottom of the page is ripped). The .SHS extension itself is invisible, as we said, so you can make it look like it is something else.
For an excellent overview of Shell Scraps, see http://www.pc-help.org/security/scrap.htm.
1. Introduction
3. The NeverShowExt registry key
Table of contents