Systems can also be put at risk from other systems they hold to be trustworthy. The computer ignores anything from the ATM that is not a legitimate transaction. No legitimate transaction can wreck the bank computer. A final precaution is to pull the plug. After all, an office system may not be worth spending great sums of money to protect if, for example, an attack will only disrupt service temporarily.
Many companies perceive no serious threat and invest accordingly.
Indeed, it is precisely the lack of good security features throughout the national information infrastructure today that leads to some confidence that computer systems could, if necessary, be made safe. Even if many systems can be taken down temporarily, it is another matter to keep them down for a long time while systems administrators work fiendishly to restore essential services. So far, most of the well-publicized hacker attacks that have been detected have been the work of amateurs not professionals. Assume their identity can be established. Conversely, it is problematic to respond violently to an information warfare attack that wasted the victim's time and money, but wounded no one.