What is the difference between safety and security?

Safety is generally thought of in terms of data integrity. Backups, checksums, etc all ensure that the data is safe from failure.

Security is protecting data from unauthorized access, such as private info being viewed by a trojan, or database tables being dropped from SQL injection.

Note that no one really really uses the word "safety" but the term "security" is widely used in the industry.

Safety references to accidentally threat. Fault tolerance deals with safety.

Security refers to intentional threat. Attacks for example!