Users receive notifications (such as Windows Toast notifications) which are undesired in a given environment. For ex.

or messages like 'Traffic from IP x.x.x.x has Been blocked', etc. and you want to hide them from the end users.
 

You need to either disable Windows toast notifications altogether, or disable notifications you do not want to be shown as per your needs in specific policies; these can be altered from the SEPM console for managed clients, or directly in the UI of the unmanaged clients.

TOAST NOTIFICATIONS

Managed Clients (on the SEPM):
(As per TechDocs's Enabling or disabling Symantec Endpoint Protection pop-up notifications that appear on Windows 8 clients)

1. In the console, on the Clients tab, on the Policies tab, under Location-specific settings, next to Client User Interface Control Settings, click Server Control.
2. Next to Server Control, click Customize.
3. In the Client User Interface Settings dialog, under General, check or uncheck Enable Windows toast notifications.
4. Click OK.

On unmanaged clients:

1. In the SEP User interface, on the Change Settings screen, under Client Management, click Configure.
2. Under Display Options, uncheck the 'Use Windows toast notifications for critical alerts'.
3. Click OK.

SPECIFIC NOTIFICATIONS

Managed clients (on the SEPM):
(As per TechDocs's Dialog Help and respective subchapters)

In the console, on the Policies tab, under following pages in a given policy:

• Virus and Spyware Protection
  • Windows Settings
    • Auto-Protect
    • Download Protection
    • Internet Email Auto-Protect
    • Microsoft Outlook Auto-Protect
    • Lotus Notes Auto-Protect (14.2 only!)
    • Miscellaneous
• Firewall
  • Windows Settings
    • Rules
• Application and Device Control
  • Application Control
    • Given Control Rule Set -> Edit
      • Given Condition -> Actions
  • Device Control

the notifications may be fine tuned (for ex. disabled) just for the specific component of a given policy, usually under a Notifications tab:

or under specific Condition for an Application Control Rule Set:

Unmanaged clients (on the SEPM):

In the SEP User interface, on the Change Settings screen, under Configure Settings, for:

• Virus and Spyware Protection
  • Auto-Protect
  • Download Insight
  • Outlook Auto-Protect
• Proactive Threat Protection
  • Behavioral Analysis
• Network and Host Exploit Mitigation
  • Notifications

the notifications may be fine tuned (for ex. disabled) just for the specific component of a given policy, usually after clicking on a Notifications button: