Hi,
You will have to disable Intrusion Preventsion System (IPS) Notifications, you can accomplish following task through SEPM console.
However I would suggest to troubleshoot further on this issue.
Blocked IP address is from internal network or it's unknown IP ?
If it's internal IP address, you can exclude IP address through IPS policy.
It is's unknown IP address, check for System vulnerability.
It is recommended to install all the Symantec features AV / PTP/ NTP with latest definitions.Always make sure that your computers are receiving definitions regularly.
You windows machines should have all the latest windows updates /Patches.
To Disable Intrusion Prevention notifications for Server Control Mode:
1. Log in to SEPM
2. Select Clients on the left
3. Choose the appropriate group
4. Select the Policies tab
5. Expand Location-Specific Settings and select Server Control next to "Client User Interface Control Settings"
6. Click the Customize button next to "Server Control"
7. Uncheck "Display Intrusion Prevention Notifications"
To Disable Intrusion Prevention Notifications in Mixed Mode:
1. Log in to SEPM
2. Click on Clients on the left
3. Choose the appropriate group
4. Click the Policies tab
5. Expand Location-Specific Settings and click Mixed Control next to "Client User Interface Control Settings"
6. Click the Customize button next to "Mixed Mode"
7. Scroll to the bottom of the list, and in the "notifications" area, click the radial in the "Server" column to give you the ability to override this option on a client.
8. Select the Client User Interface Settings tab
9. Uncheck "Display Intrusion Prevention notifications"
I hope it will help you !!!