You encounter an error message when downloading IDF 1.5 in the Plug-in Manager of OfficeScan (OSCE) 10.6 or 11.0:
An update error occured. Unable to download Plug-in Manager or the plug-in program installation package. The update source may have been changed or the installation package may have been removed from the update source. Refer to the Troubleshooting section of the online help for solutions.
The error occurs because IDF 1.5 reached its official End of Support (EOS) on September 30, 2016. For this reason, the IDF installation package has already been removed from Trend Micro's Active Update servers.
If you plan on installing IDF, you will need to install the standalone Trend Micro Vulnerability Protection (TMVP) instead. For more information on IDF EOS, refer to End of Support (EOS) for Intrusion Defense Firewall (IDF) 1.5 article.