Yosemite will only allow you to run signed executables. That by itself is the only security measure you need. In theory, a bad actor could sign an evil program

Yosemite will only allow you to run signed executables. That by itself is the only security measure you need. In theory, a bad actor could sign an evil program. In practice, that's never happened. If it did happen, the signature would be immediately revoked by Apple as soon as the issue was detected, and would then cease to be an issue.