Typing your password or credit card number into a computer is a moment’s work. But if you think your personal details disappear as soon as you hit the Return key, think again: they can sit on the computer’s hard disk for years waiting for a hacker to rip them off.

　 As people spend more time on the web and hackers become more sophisticated, the dangers of storing personal information on computers are growing by the day, security experts say. There are some safeguards, such as never allowing your computer to store your passwords. But even that is no guarantee of security.

　 When you type in a password, it is stored in random access memory (RAM), where it is held temporarily until other data overwrites it or the computer is switched off.

　 But every so often, the computer copies the contents of its RAM onto hard disk, where it is easy prey for a hacker, who can read it directly or design a worm to e-mail it back. The longer sensitive data stays in RAM, the more likely it is to be copied onto the disk, where it stays until it is overwritten—which might not happen for years.

　 Tal Garfinkel and colleagues from Stanford University have created a software tool which simulates the workings of a complete computer system. Within the simulation, sensitive data can be tagged and then tracked as it passes through the system. Next, Garfinkel and his team simulated computers running common software that regularly handles passwords or confidential personal information, such as Internet Explorer, the Windows login script and Apache server software.

　 In a paper to be presented, they conclude that the programs took virtually no measures to limit the length of time the information is retained. Some of the tested software even copied the sensitive information, apparently without restraint.

　 This is the first time anyone has tried to measure the extent of this problem, says Rebecca Wright, a security expert at Stevens Institute of Technology. Garfinkel hopes the results will arouse software developers to take action.

1．Which of the following statements is true according to the passage?

　 A．It is secure to use your password as long as you hit the Return key.

　 B．Your personal details is likely to be in danger if you spend more time on the web.

　 C．Your password will be safe if you have some safeguards.

　 D．Never allowing your computer to store your passwords will be safe.

2．Which of the following is NOT the reason for the unsafety of a password?

　 A．It will be stored in RAM.

　 B．It will be copied onto hard disk.

　 C．It might not be overwritten.

　 D．It will disappear as soon as you hit the return key.

3．Tal Garfinkel and his team measured the extent of security of　　　 .

　 A．simulating the working of a complete computer system

　 B．tagging sensitive data

　 C．passing through the system

　 D．running common software

4．What can be inferred from the passage?

　 A．The length of the time the information is stored is not limited.

　 B．The programs can not retain the information.

　 C．The security problem should be paid more attention to.

　 D．Some sensitive information has been copied.