o add or remove blocked file types by using Central Administration
Verify that you have the following administrative credentials.
You must be a farm administrator on the server.
In Central Administration, click Security.
On the Security page, in the General Security section, click Define blocked file types.
On the Blocked File Types page, if you want to change the selected web application, on the Web Application menu, click Change Web Application. Use the Select Web Application page to select a web application.
Do one of the following:
To block an additional file type, scroll to the bottom of the Type each file name extension on a separate line text box, type the file name extension that you want to block, and then click OK.