数据完整性（data integrity): 指数据在整个生命周期中的准确性、可靠性和最终有效性。它是应防止数据库中存在不符合语义规定的数据和防止因错误信息的输入输出造成无效操作或错误信息而提出的

数据隐私(Data privacy): 秘密数据，是不想被他人获取的信息。从隐私所有者的角度，可将隐私数据分为个人隐私数据和公共隐私数据，个人隐私数据包括可用来识别或定位个人的信息（如电话号码、地址、信用卡号、认证信息等）和敏感的信息（如个人的健康状况、财务信息、历史访问记录、公司的重要文件等）

数据安全(Data security): 保护信息及信息系统免受未经授权的进入、使用、披露、破坏、修改、检视、记录及销毁。

Data integrity

Only accurate and up-to-date data has data integrity.

• individual user not taking appropriate care
• internal mismanagement
• natural disasters
• unauthorised intrusion into the system by an individual
• malicious soft ware entering the system.

• One cause of concern is the hacker who is someone intent on gaining unauthorised access to a computer system.
  • A hacker who achieves this aim might gain access to private data.
  • Alternatively, a hacker might cause problems by deleting files or causing problems with the running of the system.
• The other major cause of concern is malicious soft ware entering the system.

Malware is the everyday name for malicious soft ware.

The various types of malware-containing program code are:

• virus:: tries to replicate itself inside other executable code
• worm:: runs independently and transfers itself to other network hosts
• logic bomb:: stays inactive until some condition is met
• Trojan horse:: replaces all or part of a previously useful program
• spyware:: collects information and transmits it to another system
• bot:: takes control of another computer and uses it to launch attacks.

Malware can also be classified in terms of the activity involved::

• phishing:: sending an email or electronic message from an apparently legitimate source requesting confidential information
• pharming:: setting up a bogus website which appears to be a legitimate site
• keylogger:: recording keyboard usage by the legitimate user of the system.

Many system vulnerabilities are associated directly with the activities of legitimate users of a system. Two examples which do not involve malware are as follows.

• The use of weak passwords and particularly those which have a direct connection to the user. A poor choice of password gives the would-be hacker a strong chance of guessing the password and thus being able to gain unauthorised access.
• A legitimate user not recognising a phishing or pharming attack and, as a result, giving away sensitive information.

Typical examples of actions that might introduce malware are:

• attaching a portable storage device
• opening an email attachment
• accessing a website
• downloading a file from the Internet.

Systems themselves often have security weaknesses.

1. Operating systems often lack good security. Over time, there is a tendency for operating systems to increase in complexity, which leads to more opportunities for weak security.
2. In the past, commonly used application packages allowed macro viruses to spread
3. A very specific vulnerability is buffer overflow.

Such measures come under the general heading of disaster recovery contingency planning.

If an organisation has a full system always ready to replace the normally operational one, it is referred to as a ‘hot site’. By definition, such a system has to be remote from the original system to allow recovery from natural disasters such as earthquake or flood.

organisations may need to have the original system and its replacement running in parallel for a period to ensure continuity of service.

The main security feature of a user account is the authentication of the user.

The normal method is to associate a password with each account.

In order for this to be effective the password needs a large number of characters including a variety of those provided in the ASCII scheme.

Alternative methods of authentication include biometric methods and security tokens.

• keep a personal computer secure includes not leaving the computer switched on when unattended
• not allowing someone else to observe you accessing the computer
• not writing down details of how you access it.
• Users may attach portable storage devices to a system, but this increases the risk of transferring malware into the system.

The primary defence to malware entering a system through a network connection is to install a firewall.

A firewall can inspect the system addresses identified in the transmission of data, but can sometimes also inspect the data itself to check for anything unusual or inappropriate.

insist that the sender attaches a digital signature to the email.

1. One option is to install what is normally referred to as anti-virus soft ware but which is usually aimed at combating any type of malware.
2. Another option is to install an intrusion detection system that will take as input an audit record of system use and look for examples that do not match expected system activity.

reasons for accidental loss of data:

• a disk or tape gets corrupted
• a disk or tape is destroyed
• the system crashes
• the file is erased or overwritten by mistake
• the location of the file is forgotten.

The principles for the procedure traditionally followed are straightforward::

• a full backup is made at regular intervals, perhaps weekly
• at least two generations of full backup are kept in storage
• incremental backups are made on a daily basis.

backup method:

• For maximum security the backup disks or tapes are stored away from the system in a fireproof and flood-proof location.
• This works well when an incremental backup occurs done overnight with the full backup handled at the weekend.
• One solution is to have a backup program that effectively freezes the file store while data is being copied.
• An alternative approach is to use a disk-mirroring strategy.

The solution is to have an authorisation policy which gives different access rights to different files for different individuals.

Data can be encrypted to protect.

数据验证是检查数据副本以确保其与原始数据副本完全相同的过程。备份数据后，通常需要进行数据验证。大多数现代备份软件都有内置的验证功能。

数据验证是一个非常重要的过程，因为它使您感到安全，因为您将确信您可以实际使用备份的数据，以防原始数据丢失或损坏。验证软件通常确保副本可读，并且内容与原始内容完全匹配。

但通常大型企业在夜间执行自动备份，因此由于验证过程而导致的时间延长并不是一个严重的问题。

Validation can only prevent incorrect data if there is an attempt to input data that is of the wrong type, in the wrong format or out of range.

Typical examples are:

• a presence check to ensure that an entry field is not left blank
• a format check, for example a date has to be dd/mm/yyyy
• a length check, for example with a telephone number
• a range check, for example the month in a date must not exceed 12
• a limit check, for example a maximum number of years for a person’s age
• a type check, for example only a numeric value for the month in a date
• an existence check, for example that a file exists with the filename referred to in the data entry.

1. Double entry is one method of verification. The most common example is when a user is asked to supply a new password.
2. A second method is to use a visual check of what has been entered.

When a series of numbers are used to identify something, it is possible to use a check digit method of verification.

It is possible for data to be corrupted during transmission. Verification techniques need to check on some property associated with the bit pattern.

The sum of these binary numbers in a block is calculated and supplied as a checksum value in the transmission.

an error can be detected but its position in the transmission cannot be determined.