A Security Event is any observable occurrence in a system or network. Examples of an event are: 

• A user connecting to a file share,
• A server receiving a request for a web page,
• A user sending email, and
• A firewall blocking a connection attempt.
• System crashes,
• Packet floods,
• Unauthorized use of system privileges,
• Unauthorized access to sensitive data, and
• Execution of malware that destroys data.