Executable email attachments -- Educate the end user
This tip was submitted to the searchSecurity Tip Exchange by user Rick Pierides. Let other users know how useful it is by rating the tip below.
I work with a lot of clients who cannot afford the luxury of expensive filtering software for their email. So when I make my visits I often take a little bit of extra, gratis time to educate end users on types of executables, how Windows parses the extensions from attachment filenames and how the bad guys attempt to hide the real extension. I like to hand out small post up-sized stickers with a listing of the more common executable extensions as a reminder. Along with current virus signatures and disabling Windows Scripting Host, this has gone a long way toward a much safer and more aware environment for my clients and their employees.
* Windows defines the file type by the letters after the last period; i.e., DIAMONDINV.TXT.vbs
* Lower case extensions can make you miss the real extension. Look!
* The icon should match the file type you are expecting.
* Watch for the ellipses to indicate padded spaces to hide the real extension. DIAMOND.TXT ...
Extensions to be very wary of:
EXE, COM, BAT: Native executables
VBS, VBE: Visual Basic Scripts
HTA: HTML Application
REG: Registry Files
SHS: Scrap Objects
DOC,XL, XLS, XLA: Office files that might contain Macros
CSLID: Refers to registered controls
A searchSecurity user sent in this comment on Rick's tip:
In regards to Executable e-mail attachments -- Educate the end user, I would only add that it is important to make sure Windows is NOT set to hide file extensions for known file types! Otherwise, there's a good chance you won't read the file extension.