A cracker might start a program that searches every system on the Internet for a particular security hole. When the program discovers a machine with that hole, it connects to the machine and downloads all the passwords, and then it proceeds to check other machines. Unfortunately, it takes a lot of time to keep up with this information and apply all of the appropriate patches. People One of the more common threats to security is the human being. People can make mistakes which cause the integrity of data to be questioned, weaken the physical security of computer systems, or even cause systems to crash.
Some people intentionally cause security problems.
These kinds of people are called hackers or crackers. They could also be disgruntled employees. Other kinds of people weaken security through negligence. These kinds of people share their computer accounts, share their computer passwords, choose bad passwords, don't back-up their files, don't lock their office doors, don't log out when away from their computers, etc. This person is unavailable for extended periods due to illness, termination or even death.