Security

Unix model
Quite weak
Look at bugtraq
Buffer overflows: CERT Advisory CA-2001-33 Multiple Vulnerabilities in WU-FTPD (November 29, 2001)
SUID exploits

Where the exploits come from
Daemons must run as root to access certain resources
Processes cannot raise their permission in the system (only lower it)
Kernel's fault

Traditional security model is too limited