📚 Cybersecurity Key Concepts for IB & Edexcel Computer Science | IB Edexcel 计算机：网络安全考点精讲
Cybersecurity is a fundamental component of both the IB and Edexcel Computer Science syllabi. It encompasses the techniques used to protect computer systems, networks, and data from digital attacks, theft, and damage. Understanding threats, vulnerabilities, and the countermeasures is crucial for any student aiming to master this topic.
网络安全是 IB 和 Edexcel 计算机科学课程的基本组成部分。它涵盖的保护计算机系统、网络和数据免受数字攻击、盗窃和破坏的技术。理解威胁、漏洞和应对措施对于任何想要掌握这一主题的学生都至关重要。
1. Introduction to Cybersecurity | 网络安全概述
Cybersecurity refers to the practice of defending computers, servers, mobile devices, electronic systems, networks, and data from malicious attacks. The core objectives include ensuring confidentiality, integrity, and availability of information—often referred to as the CIA triad. As digital transformation accelerates, the attack surface expands, making security education essential.
网络安全指的是保护计算机、服务器、移动设备、电子系统、网络和数据免受恶意攻击的实践。其核心目标包括确保信息的机密性、完整性和可用性——通常被称为 CIA 三元组。随着数字化转型加速，攻击面不断扩大，安全教育变得至关重要。
2. Malware: Viruses, Worms, Trojans | 恶意软件：病毒、蠕虫、特洛伊木马
Malware, short for malicious software, is any program designed to harm or exploit a system. A virus attaches itself to a legitimate file and requires user interaction to spread. Worms replicate independently across networks without needing a host file. Trojans disguise themselves as useful software but deliver a malicious payload, such as creating backdoors or stealing data.
恶意软件是旨在伤害或利用系统的任何程序。病毒将自身附加到合法文件上，并需要用户交互才能传播。蠕虫可以独立地在网络中复制，无需宿主文件。特洛伊木马伪装成有用的软件，但会传递恶意负载，例如创建后门或窃取数据。
3. Ransomware and Spyware | 勒索软件与间谍软件
Ransomware encrypts the victim’s files and demands a ransom payment, usually in cryptocurrency, to restore access. Notable examples include WannaCry and CryptoLocker. Spyware secretly monitors user activity and gathers sensitive information such as passwords, browsing habits, and credit card details without consent.
勒索软件会加密受害者的文件，并要求支付赎金（通常以加密货币形式）以恢复访问权限。著名的例子包括 WannaCry 和 CryptoLocker。间谍软件会秘密监视用户活动，并在未经同意的情况下收集密码、浏览习惯和信用卡详细信息等敏感信息。
4. Social Engineering Attacks | 社会工程学攻击
Social engineering exploits human psychology rather than technical vulnerabilities. Attackers manipulate individuals into breaking normal security procedures. Common techniques include pretexting, baiting, and tailgating. The strongest firewall is useless if an employee willingly gives away their credentials.
社会工程学利用人类心理而非技术漏洞进行攻击。攻击者操纵个人违反正常的安全规程。常见的技术包括借口法、钓鱼诱饵和尾随进入。如果员工愿意交出凭证，再强大的防火墙也无用。
5. Phishing and Shoulder Surfing | 网络钓鱼与肩窥
Phishing involves sending fraudulent emails or messages that appear to come from reputable sources to steal login credentials or install malware. Variants include spear phishing (targeted) and whaling (aimed at executives). Shoulder surfing is a low-tech method where an attacker watches the victim type passwords or PINs over their shoulder.
网络钓鱼涉及发送看似来自信誉良好的来源的欺诈性电子邮件或消息，以窃取登录凭据或安装恶意软件。变种包括鱼叉式网络钓鱼（有针对性的）和捕鲸式钓鱼（针对高管）。肩窥是一种低技术含量的方法，攻击者从受害者背后偷看其键入密码或 PIN 码。
6. Network-based Attacks: DoS and DDoS | 基于网络的攻击：DoS 与 DDoS
A Denial of Service (DoS) attack floods a server or network with traffic to exhaust resources and deny service to legitimate users. A Distributed DoS (DDoS) uses many compromised computers (a botnet) to launch the attack simultaneously, making it much harder to mitigate. These attacks impact the availability element of the CIA triad.
拒绝服务攻击（DoS）会使用流量淹没服务器或网络，耗尽资源并拒绝向合法用户提供服务。分布式拒绝服务攻击（DDoS）利用许多受感染的计算机（僵尸网络）同时发起攻击，使其更难缓解。这些攻击影响了 CIA 三元组中的可用性要素。
7. Man-in-the-Middle Attacks | 中间人攻击
In a Man-in-the-Middle (MitM) attack, the attacker intercepts and possibly alters the communication between two parties who believe they are directly communicating. This can be achieved through ARP spoofing, DNS spoofing, or by setting up a rogue Wi-Fi hotspot. Encryption protocols like TLS are designed to prevent MitM by authenticating endpoints.
在中间人攻击（MitM）中，攻击者截取并可能更改两方之间的通信，而双方都认为他们在直接通信。这可以通过 ARP 欺骗、DNS 欺骗或设置恶意 Wi-Fi 热点来实现。TLS 等加密协议旨在通过对端点进行身份验证来防止中间人攻击。
8. Data Interception and Theft | 数据截获与盗窃
Data interception involves capturing data packets as they travel across a network. Packet sniffers can be used for legitimate network analysis or maliciously to steal unencrypted data. SQL injection is another theft mechanism where an attacker inserts malicious SQL statements into an input field to manipulate the database and extract sensitive records.
数据截获涉及在数据包通过网络传输时捕获它们。数据包嗅探器可用于合法的网络分析，也可恶意用于窃取未加密的数据。SQL 注入是另一种盗窃机制，攻击者将恶意的 SQL 语句插入输入字段，以操纵数据库并提取敏感记录。
9. Encryption: Symmetric and Asymmetric | 加密：对称加密与非对称加密
Encryption converts plaintext into ciphertext using an algorithm and a key. Symmetric encryption uses the same key for both encryption and decryption (e.g., AES). Asymmetric encryption uses a pair of keys: a public key for encryption and a private key for decryption (e.g., RSA). Asymmetric encryption solves the key distribution problem but is computationally slower.
加密使用算法和密钥将明文转换为密文。对称加密使用相同的密钥进行加密和解密（例如 AES）。非对称加密使用一对密钥：公钥用于加密，私钥用于解密（例如 RSA）。非对称加密解决了密钥分发问题，但计算速度较慢。
10. Firewalls and Proxy Servers | 防火墙与代理服务器
A firewall monitors and controls incoming and outgoing network traffic based on predetermined security rules. It can be hardware-based, software-based, or a combination of both. A proxy server acts as an intermediary between a client and the internet, hiding the client’s IP address, filtering content, and caching frequently accessed data to improve performance.
防火墙根据预定的安全规则监视和控制传入和传出的网络流量。它可以是基于硬件的、基于软件的或两者的结合。代理服务器充当客户端和互联网之间的中介，隐藏客户端的 IP 地址、过滤内容并缓存经常访问的数据以提高性能。
11. Authentication and Access Control | 身份验证与访问控制
Authentication verifies the identity of a user, while access control determines what resources an authenticated user can use. Methods include passwords, biometrics (fingerprint, facial recognition), and multi-factor authentication (MFA), which combines two or more different factors such as something you know, something you have, and something you are.
身份验证验证用户的身份，而访问控制确定经过身份验证的用户可以使用哪些资源。方法包括密码、生物识别（指纹、面部识别）和多因素身份验证（MFA），它结合了两种或多种不同的因素，例如你知道的东西、你拥有的东西和你本人的特征。
12. Security Policies and Ethical Hacking | 安全策略与道德黑客
A security policy outlines how an organisation protects its information assets. It includes acceptable use policies, password rules, and incident response procedures. Penetration testing, performed by ethical hackers, simulates attacks to identify vulnerabilities before real attackers can exploit them. This proactive approach is an essential part of modern cyber defence strategies.
安全策略概述了组织如何保护其信息资产。它包括可接受使用策略、密码规则和事件响应程序。渗透测试由道德黑客执行，模拟攻击以在真正的攻击者利用漏洞之前识别漏洞。这种主动方法是现代网络防御策略的重要组成部分。
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