InterScan Web Security Virtual Appliance (IWSVA) provides the "Scan before delivering" feature in order to prevent the client web browser from timing out in IWSVA scanning large files.
However, this may cause inconvenience in certain cases.
IWSVA provides the following methods to address large file scan lag.
You can set them in HTTP > Advanced Threat Protection > Policies > Virus/Malware Scan Rule.
- Scan before delivering: The client browser shows the scan progress screen until IWSVA completes the scan.
- Deferred scanning: IWSVA delivers a certain amount of the file to the client browser while scanning the file.
The following could occur if you use "Scan before delivering" because IWSVA sends the information of the scan progress screen:
- The update operation for Microsoft Windows Update/Adobe software fails because the updater (browser plugin / Windows Update process) cannot deal with the information of the scan progress screen.
- Certain dynamic web content cannot be shown as expected because the information of the scan progress screen hinders the display of the correct content.
Note: IWSVA 6.5 already includes the URLs for Windows Updates in Global Trusted URLs.
If you encounter these issues, consider doing either of the following:
Use Deferred scanning instead of Scan before delivering.
IWSVA does not send the scan progress screen in this case, which can address the issues.
Add the URLs to Global Trusted URLs.
The URLs in the Global Trusted URLs bypass the IWSVA's scan, which can address the issues.
For example, the following should be added as "Web site" entry for Adobe software: