问题 单项选择题

许多黑客利用缓冲区溢出漏洞进行攻击,对于这一威胁,最可靠的解决方案是()。

A.安装防火墙

B.安装用户认证系统

C.安装相关的系统补丁软件

D.安装防病毒软件

答案

参考答案:C

解析:

缓冲区溢出攻击是利用目标程序的缓冲区溢出漏洞,通过操作目标程序堆栈并暴力改写其返回地址,从而获得目标控制权。其原理是向一个有限空间的缓冲区中复制过长的字符串,从而导致这一过长的字符串覆盖了相邻的存储单元而造成程序瘫痪、系统重启等现象;同时可让攻击者运行恶意代码,执行任意指令,以及获得超级权限等。

由于这种攻击方式所传输的数据分组并无异常特征,没有任何欺骗,以及用来实施缓冲区溢出攻击的字符串的多样化,无法与正常数据有效地进行区分。因此防火墙对这种攻击方式无能为力。另外,因为这种攻击方式不是一种窃密和欺骗的手段,而是从计算机系统的最底层发起攻击,所以在它的攻击下系统的身份验证和访问权限等安全策略形同虚设。这就要求系统管理员或普通用户及时为操作系统和应用程序更新补丁程序,并通过减少不必要的开放服务端口等措施来降低因缓冲区溢出而造成的攻击损失。

阅读理解

A poor farmer had a  friend who was famous for the wonderful apple trees he grew.

One day, his friend gave the farmer a young apple tree and told him to plant it.  The farmer was pleased with the gift, but he did not know where to plant it.

He was afraid that if he planted the tree near the road, strangers would steal the fruit.  If he planted the tree in one of his fields, his neighbors would come at night and steal some of the apples.  If he planted the tree near his house, his children would take the fruit.  Finally he planted the tree in his wood.  But without sunlight and good soil(土壤), the tree soon died.

Later the friend asked the farmer why he had planted the tree in such a poor place.  “What’s the difference?” the farmer said angrily and then told what he had thought.

“Yes,” said the friend, “but at least someone could have enjoyed the fruit.  Now you not only have robbed everyone of the fruit, but also you have destroyed (毁掉) a good apple tree! ”

小题1:What gift did the farmer get from his friend one day?

___________________________________________________________

小题2:How many people are there in the story?

____________________________________________________________

小题3:Where did the farmer plant the apple tree at last?

____________________________________________________________

小题4:Why did the apple tree soon die?

____________________________________________________________

小题5:Who destroyed the apple tree?

____________________________________________________________

多项选择题