Virus definition not updating
The issue causing the update issue may be resolved by the improved processing and enhanced features available in a software version later than what is running.What you need: 1) Latest Certified Definitions from Symantec.
Technologies designed to block attacks just as they transition from the network cable or wireless network to the computer, before they have a chance to establish residency in a physical file on a user’s computer. Behavioral-based protection technology observes actively running threats on your computer and can terminate running programs if they exhibit malicious behaviors; this technology provides proactive protection from entirely new, previously unseen attacks.
This will initiate a Windows Defender update which, hopefully, will be successful.
If all else fails, you can try downloading the latest update package for Windows Defender manually as a last resort. Wait for the update package to be fully downloaded.
Step 2) Live Update Installer Assume the wrong Live Update version is installed on the system, locate the Live Update installer shipped with your release of SEP as per above.
Step 3) Remove Live Update and install the correct version for SEP - Uninstall "Symantec Live Update" from the Windows Control Panel, - Reboot the server, - Install the Live Update shipped with your release of Endpoint Protection.