chap19security安全

1、Applied Operating System Concepts,Chap 19: Security安全,Applied Operating System Concepts,Content (內(nèi)容),The Security Problem（安全問題）Authentication（授權(quán)）Program Threats（來自程序的威脅）System Threats（來自系統(tǒng)的威脅）Threat Monitoring（威脅的監(jiān)

2、控）Encryption（加密）Computer-Security Classifications(計(jì)算機(jī)安全的分級 )Summary（總結(jié)）,Applied Operating System Concepts,The Security Problem（安全問題）,Security must consider external environment of the system, and protect it from:（安全必須

3、考慮系統(tǒng)的外環(huán)境，以下方面防護(hù)：）unauthorized access.（未授權(quán)訪問）malicious modification or destruction（惡意的修改和破壞）accidental introduction of inconsistency.（意外的引入和不一致）Easier to protect against accidental than malicious misuse.（防止意外的誤用比防止惡意的

4、誤用更加容易）,Applied Operating System Concepts,Authentication（授權(quán)）,User identity most often established through passwords, can be considered a special case of either keys or capabilities.（用戶身份通常使用密碼確立，可以認(rèn)為密碼就是某種權(quán)限或者鑰匙）Passwor

5、ds must be kept secret.（密碼必須保持秘密的狀態(tài)）Frequent change of passwords.（經(jīng)常更換密碼）Use of “non-guessable” passwords.（使用難猜的密碼）Log all invalid access attempts.（記錄所有非法訪問企圖）,Applied Operating System Concepts,Program Threats（程序的威脅）,

6、Trojan Horse（特洛伊木馬）Code segment that misuses its environment.（代碼段濫用環(huán)境）Exploits mechanisms for allowing programs written by users to be executed by other users.（利用機(jī)制使得某個(gè)用戶寫的程序可以被其他用戶運(yùn)行）Trap Door（后門）Specific user ident

7、ifier or password that circumvents normal security procedures.（特殊的用戶標(biāo)識符或者密碼可以繞過通常的安全檢查）Could be included in a compiler.（有可能包含在編譯器中）,Applied Operating System Concepts,System Threats（系統(tǒng)的威脅）,Worms – use spawn mechanism; st

8、andalone program（蠕蟲：使用大量復(fù)制機(jī)制；獨(dú)立的程序）Internet worm（因特網(wǎng)蠕蟲）Exploited UNIX networking features (remote access) and bugs in finger and sendmail programs.（使用UNIX網(wǎng)絡(luò)特性以及finger、sendmail等程序的漏洞）Grappling hook program uploaded mai

9、n worm program.（掛鉤程序啟動蠕蟲程序的主體）Viruses – fragment of code embedded in a legitimate program.（病毒：嵌入到合法程序中的代碼片斷）Mainly effect microcomputer systems.（主要影響微機(jī)系統(tǒng)）Downloading viral programs from public bulletin boards or excha

10、nging floppy disks containing an infection.（從網(wǎng)絡(luò)下載帶毒程序或者使用受到感染的軟盤）Safe computing.（安全計(jì)算）,Applied Operating System Concepts,The Morris Internet Worm（Morris因特網(wǎng)蠕蟲）,Applied Operating System Concepts,Threat Monitoring（威脅監(jiān)控）,C

11、heck for suspicious patterns of activity – i.e., several incorrect password attempts may signal password guessing.（檢查可疑的行動模式：例如，多次錯(cuò)誤的密碼嘗試可能表示有人在猜密碼）Audit log – records the time, user, and type of all accesses to an obje

12、ct; useful for recovery from a violation and developing better security measures.（審計(jì)日志：記錄所有對象訪問的時(shí)間、用戶、以及類型；對于受損后的恢復(fù)以及開發(fā)更好的安全措施有用）Scan the system periodically for security holes; done when the computer is relatively unus

13、ed.（定期掃描系統(tǒng)安全漏洞；系統(tǒng)不用的時(shí)候關(guān)閉）,Applied Operating System Concepts,Threat Monitoring (Cont.)（威脅監(jiān)控 續(xù)）,Check for:（檢查）Short or easy-to-guess passwords（過短的或易猜的密碼）Unauthorized set-uid programs（未授權(quán)的set-uid程序）Unauthorized programs

14、 in system directories（系統(tǒng)目錄中的未授權(quán)程序）Unexpected long-running processes（程序的意外超常時(shí)間運(yùn)行）Improper directory protections（不恰當(dāng)?shù)哪夸洷Ｗo(hù)）Improper protections on system data files（不恰當(dāng)?shù)南到y(tǒng)數(shù)據(jù)文件保護(hù)）Dangerous entries in the program search

15、path (Trojan horse)（危險(xiǎn)的程序搜索路徑入口）Changes to system programs: monitor checksum values（系統(tǒng)程序的改變：監(jiān)控器檢查程序代碼的校驗(yàn)和）,Applied Operating System Concepts,Network Security Through Domain Separation Via Firewall網(wǎng)絡(luò)安全通過使用防火墻分離的域?qū)崿F(xiàn),Appl

16、ied Operating System Concepts,Encryption（加密）,Encrypt clear text into cipher text.（加密使得明文變成密文）Properties of good encryption technique:（優(yōu)秀加密技術(shù)的特征）Relatively simple for authorized users to incrypt and decrypt data. （對于授權(quán)用

17、戶，加密和解密都相對的簡單）Encryption scheme depends not on the secrecy of the algorithm but on a parameter of the algorithm called the encryption key.（加密模式依賴于算法的密鑰參數(shù)，而不是算法的保密）Extremely difficult for an intruder to determine the en

18、cryption key.（入侵者確定密鑰極為困難）Data Encryption Standard substitutes characters and rearranges their order on the basis of an encryption key provided to authorized users via a secure mechanism. Scheme only as secure as the m

19、echanism. （數(shù)據(jù)加密標(biāo)準(zhǔn)使用通過安全機(jī)制提供給授權(quán)用戶的密鑰代替了打亂次序文字串。模式和機(jī)制一樣安全）,Applied Operating System Concepts,Encryption (Cont.)（加密 續(xù)）,Public-key encryption based on each user having two keys:（公鑰加密，每個(gè)用戶有兩個(gè)密鑰）public key – published key use

20、d to encrypt data.（公鑰：用于加密的公共密鑰）private key – key known only to individual user used to decrypt data.（私鑰：用于解密的密鑰，只有授權(quán)的用戶個(gè)人知道）Must be an encryption scheme that can be made public without making it easy to figure out the

21、 decryption scheme.（加密模式必須可以公開，并且不會因此容易計(jì)算出來）Efficient algorithm for testing whether or not a number is prime.（高效的算法測試一個(gè)數(shù)是否為素?cái)?shù)）No efficient algorithm is know for finding the prime factors of a number.（大數(shù)的質(zhì)因數(shù)分解目前只有復(fù)雜度很高的

22、算法）,Applied Operating System Concepts,Computer-Security Classifications(計(jì)算機(jī)安全的分級 ),Four divisions of security : A,B,C,and D. The lowest-level classifications is division D,or minimal protection.(安全有四級A,B,C,D，其中D的等級最低，或者

23、保護(hù)性最小。)Division D comprises only one class,failed to meet the requirements of any one of the other security classes.MS-DOS and Windows 3.1 are in division D.（D僅是一個(gè)級別，不滿足其他安全級別的需要。MS-DOS和Win3.1是D級別）,Applied Operating Sys

24、tem Concepts,Computer-Security Classifications(Cont.)(計(jì)算機(jī)安全的分級 續(xù) ),Division C has two levels:C1 and C2.（C有兩個(gè)級別C1和C2）A C1 class system incorporates some form of controls the allow users to protect private information an

25、d to keep other users from accidentally reading or destroying their data. Most version of UNIX are C1 class.(C1級別系統(tǒng)包含一些形式的控制，允許用戶保護(hù)他們的私人信息，防止其他用戶意外地讀或破壞他們的數(shù)據(jù)。大部分版本的UNIX都是C1級別)A C2 class system adds to the requirements o

26、f a C1 system via an individual-level access control.Some special,secure versions of UNIX have been certified at the C2 level.（C2級別系統(tǒng)通過個(gè)體級別地訪問控制，在C1系統(tǒng)上增加了一些需求。一些特殊的安全版本的UNIX被授予C2級別）,Applied Operating System Concepts,Comp

27、uter-Security Classifications(Cont.)(計(jì)算機(jī)安全的分級 續(xù) ),Division B mandatory-protection systems have all the properties of a class C2 system, plus they attach sensitivity labels to each object. Division B has three levels:B1,

28、B2 and B2.（B類是一個(gè)強(qiáng)制保護(hù)性系統(tǒng)，具有所有C2類系統(tǒng)的屬性，另外為每個(gè)對象都貼上敏感的標(biāo)簽。B有三個(gè)級別B1,B2和B3）Division A is the highest-level classification.(A 類是最高等級的分類。),Applied Operating System Concepts,Java Security Model（Java的安全模型）,Applied Operating System

29、 Concepts,Summary（總結(jié)）,In this chapter, we examine the ways in which information may be misused or intentionally made inconsistent. （本章我們分析了信息可能被誤用或故意使之不一致的方法）We then present mechanisms to guard against this occurrence.（