Assume that you use Microsoft Lync Server 2010 Control Panel to set the global file transfer filter to Block all. In this situation, you can still send files that have a file name that uses a double-byte character set and that contains more than 8 characters.
To resolve the issue, install the following cumulative update:
2737915 Description of the cumulative update for Lync Server 2010: October 2012
For more information about how to change the default file transfer filter, go to the following Microsoft website: