This issue may occur due to the special file handling feature of the HTTP scanning in IWSS/IWSVA. To prevent it from occurring, you can add the relevant URLs to the scan exception list.

IWSS 3.1 for Linux & IWSVA 5.6

1. Create a backup copy of the /etc/iscan/intscan.ini file.
2. Open the intscan.ini file in a text editor.
3. Under [http], add the following to the "client_skip_content" parameter for Windows Update:

   client_skip_content=Host: windowsupdate.microsoft.com,Host:
   v5.windowsupdate.microsoft.com,Host:
   v4.windowsupdate.microsoft.com,Host: download.windowsupdate.com,Host:
   windowsupdate.com,Host: office.microsoft.com,Host:
   update.microsoft.com,Host: www.download.windowsupdate.com
   For Adobe Download Manager:
   client_skip_content=Host: ardownload.adobe.com,Host:
   download.adobe.com

4. Save and close the file.
5. Run the following commands to restart the HTTP daemon:

   #/etc/rc#.d/S99IWSS stop
   #/etc/rc#.d/S99IWSS start

IWSS 3.1 for Windows

1. Create a backup copy of the <IWSS installation folder>\intscan.ini file.
2. Open the intscan.ini file in a text editor.
3. Under [http], add the following to the "client_skip_content" parameter for Windows Update:

   client_skip_content=Host: windowsupdate.microsoft.com,Host:
   v5.windowsupdate.microsoft.com,Host:
   v4.windowsupdate.microsoft.com,Host: download.windowsupdate.com,Host:
   windowsupdate.com,Host: office.microsoft.com,Host:
   update.microsoft.com,Host: www.download.windowsupdate.com
   For Adobe Download Manager:
   client_skip_content=Host: ardownload.adobe.com,Host:
   download.adobe.com

4. Save and close the file.
5. Restart the Trend Micro InterScan Web Security Suite for HTTP service.