Some hackers do get caught, but many use tools to hide their digital footprints. In many cases, once a hacker is able to exploit a security vulnerability in a software program to gain access to computer or network, he can continue accessing that system undetected for many months or even years. Security systems look for unusual activity, so hackers find ways to mask their operation as legitimate. For instance, most company workstations send and receive data from various locations on the Internet all day long. If a hacker can gain access to an employee’s machine, he can use that system to slowly transmit company information to an off-site computer, making it look like any other regular work transmission. Unless the hacker is foolish enough to send the data directly to his own home, even if his presence is detected, determining who was behind the attack can be very difficult if not impossible.