MIME sniffing is a process that examines the content of a MIME file to determine its
context-whether it is a data file, an executable file, or some other type of file. This policy
setting determines whether Internet Explorer MIME sniffing will prevent promotion of a
file of one type to a more dangerous file type. Note- This policy setting works in conjunction
with, but does not replace, the Consistent MIME Handling settings. The recommended state
for this setting is- Enabled.
MIME file-type spoofing is a potential threat to your organization. It is recommended that
you ensure these files are consistently handled to help prevent malicious file downloads
that may infect your network.
SolutionTo implement the recommended configuration state, set the following Group Policy setting
Computer Configuration\Administrative Templates\Windows Components\Internet
Explorer\Security Features\Mime Sniffing Safety Feature\Internet Explorer Processes
Impact-When set to Enabled, MIME sniffing will not promote a file of one type to a more dangerous
file type. If you disable this policy setting, MIME sniffing configures Internet Explorer
processes to allow promotion of a file from one type to a more dangerous file type. For
example, a text file could be promoted to an executable file, which is dangerous because
any code in the supposed text file would be executed.