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Security Infrastructure Flashcards

1
Q

What is port 21 used for?

A

FTP – TCP – used to transfer files between computers.

FTP 文件传输协议，用来在电脑之间传文件（像上传、下载）。

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2
Q

What is port 22 used for?

A

SSH – TCP – used for secure remote login to servers.

SSH 安全远程登录协议，像用命令行远程控制服务器，很安全。

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3
Q

What is port 23 used for?

A

Telnet – TCP – used for remote login, but not secure.

Telnet 远程登录协议，数据是明文的，很不安全，已经淘汰。

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4
Q

What is port 25 used for?

A

SMTP – TCP – used to send emails.

SMTP 发送邮件用的协议，常用于发邮件服务器之间通信。

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5
Q

What is port 53 used for?

A

DNS – TCP/UDP – used to turn website names into IP addresses.

DNS 域名解析，把网址（例如 google.com）转换成 IP 地址。

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6
Q

What is port 80 used for?

A

HTTP – TCP – used for browsing regular (non-encrypted) websites.

HTTP 协议，用来打开普通网页（没有加密）。

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7
Q

What is port 443 used for?

A

HTTPS – TCP – used for secure websites (encrypted).

HTTPS 是加密版的 HTTP，用来打开安全网页，比如银行网站。

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8
Q

What is port 110 used for?

A

POP3 – TCP – used to receive email and download it to your device.

POP3 是旧版收邮件协议，收到邮件后就下载到本地。

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9
Q

What is port 143 used for?

A

IMAP – TCP – used to read email without downloading it.

IMAP 是新版收邮件协议，邮件保存在服务器上，可以多设备同步。

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10
Q

What is port 3389 used for?

A

RDP – TCP – used for remote desktop access to Windows systems.

RDP 是远程桌面协议，用来远程操作 Windows 电脑。

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11
Q

What is a firewall?

A

A firewall is a device or software that controls network traffic based on rules.

防火墙是控制网络流量的设备或软件，根据规则允许或阻止连接。

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12
Q

What is the main function of a firewall?

A

To block unauthorized access and allow safe traffic.

防止未经授权的访问，同时允许合法流量通过。

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13
Q

What is a packet filtering firewall?

A

It checks IP addresses and port numbers, but not content.

它只检查 IP 和端口，不看数据内容，工作在第4层。

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14
Q

What is a stateful firewall?

A

It tracks connection status and allows return traffic for valid sessions.

它会“记住连接”，允许合法请求返回的数据通过。

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15
Q

What is a proxy firewall?

A

It makes requests on behalf of the user and filters traffic at the application layer.

它代表用户与外部通信，能看懂内容，过滤更精准。

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16
Q

What is a Next-Generation Firewall (NGFW)?

A

It adds deep packet inspection, application control, and built-in IPS.

比普通防火墙更强大，可以检查数据内容、识别 App，还能防攻击。

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17
Q

What is a Web Application Firewall (WAF)?

A

A firewall that protects websites from attacks like SQL injection and XSS.

专门保护网站，能防止 SQL 注入、跨站脚本等攻击。

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18
Q

What is a screened subnet (DMZ)?

A

A separate network zone that hosts public services and isolates them from internal systems.

放网站服务器的“中间地带”，跟内网隔开，防止被入侵波及。

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19
Q

What is the difference between Layer 4 and Layer 7 firewalls?

A

Layer 4 checks ports/protocols; Layer 7 checks app-level content like URLs.

第4层看端口和协议，第7层能看懂网页内容或App行为。

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20
Q

What’s a key takeaway about firewalls?

A

Firewalls enforce rules to protect the network—some are basic, others are advanced with app awareness and attack prevention.

防火墙通过规则保护网络，有的简单，有的能识别应用甚至防攻击。

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21
Q

What is an Access Control List (ACL)?

A

A set of rules used by firewalls to allow or deny traffic.

ACL 是一组防火墙规则，用来决定哪些流量可以通过，哪些要被拦。

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22
Q

What are the common components of an ACL rule?

A

Source IP, destination IP, port, and action (allow/deny).

来源 IP、目标 IP、端口号、允许或拒绝的动作。

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23
Q

Why is rule order important in ACLs?

A

The firewall checks rules top-down and stops at the first match.

规则是从上往下执行的，遇到匹配的就不再继续查了。

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24
Q

What is the best practice for ACL rule order?

A

Put specific rules first and general “deny all” last.

越具体的规则越往上放，最底下一般是“全部拒绝”。

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25
What does “implicit deny” mean in firewalls?
If no rules match, traffic is denied by default. ## Footnote 如果没有匹配到规则，默认就拒绝这条流量（不需要你手动写）。
26
How can ACLs be configured?
Using either a web interface (GUI) or command line (CLI). ## Footnote 可以通过图形界面（像网页）或命令行界面来配置。
27
What’s the purpose of logging in firewall configuration?
To track blocked traffic and troubleshoot issues. ## Footnote 记录被拦的流量，方便排错和安全审计。
28
What happens if multiple ACL rules match a packet?
Only the first matching rule is applied. ## Footnote 只执行第一条匹配到的规则，后面的忽略。
29
What is a “deny all” rule used for?
To block all traffic that wasn’t explicitly allowed. ## Footnote 拦住所有没有被允许的流量，是最后的安全底线。
30
What’s a key takeaway about firewall rule configuration?
Rule order matters a lot—firewall rules are like traffic signs, one mistake can block everything. ## Footnote 规则顺序特别重要，像路标一样，顺序错了可能全网都不通。
31
What is an IDS?
IDS (Intrusion Detection System) detects suspicious traffic and sends alerts. ## Footnote IDS 是入侵“检测”系统，发现可疑流量后会报警，但不会拦。
32
What is an IPS?
IPS (Intrusion Prevention System) detects and blocks malicious traffic. ## Footnote IPS 是入侵“防御”系统，发现威胁后会直接阻止它进入。
33
What’s the difference between IDS and IPS?
IDS only alerts; IPS alerts and blocks. ## Footnote IDS 只报警，IPS 会拦截。一个是观察者，一个是战斗者。
34
What are the main types of IDS?
NIDS (Network), HIDS (Host), WIDS (Wireless). ## Footnote 网络型 IDS（NIDS）、主机型（HIDS）、无线型（WIDS）。
35
What does a NIDS monitor?
Traffic across the whole network. ## Footnote NIDS 监控整个网络的流量，像个“交通摄像头”。
36
What does a HIDS monitor?
Activity on a specific computer or server. ## Footnote HIDS 监控某台设备内部的行为，比如文件被改、进程异常等。
37
What is signature-based detection?
It looks for known attack patterns. ## Footnote 它靠数据库识别“已知攻击”，像查杀毒软件的病毒库。
38
What is anomaly-based detection?
It detects behavior that’s different from normal patterns. ## Footnote 它通过比较“平时行为”和“现在行为”发现异常。
39
How is an IDS usually deployed?
In passive mode—traffic is mirrored to it for monitoring. ## Footnote IDS 是旁路监听，复制一份流量来看，不影响原始通道。
40
What’s the key takeaway about IDS and IPS?
IDS watches and alerts; IPS steps in to block—use both for layered defense. ## Footnote IDS 是眼睛，IPS 是盾牌，配合使用最安全。
41
What is a load balancer?
It distributes traffic across multiple servers to prevent overload. ## Footnote 它把访问请求平均分配给多台服务器，防止某台被挤爆。
42
What does a proxy server do?
It forwards requests on behalf of users and can filter or cache content. ## Footnote 它代替用户发请求，可做内容过滤、加速、隐藏 IP。
43
What is a jump server (jump box)?
A secure gateway used by admins to access internal systems. ## Footnote 管理员登录服务器前必须先通过的中转机，提高安全性和审计能力。
44
What does a network sensor do?
It monitors and analyzes traffic to detect unusual activity. ## Footnote 它用来“监听”流量，发现异常行为，是 IDS 的好搭档。
45
What’s the purpose of a proxy cache?
It saves copies of frequently accessed content to speed up requests. ## Footnote 缓存常访问的网页或文件，提高访问速度，节省带宽。
46
What is the difference between a load balancer and a proxy?
Load balancer splits traffic across servers; proxy forwards client requests. ## Footnote 负载均衡器分发“服务端”，代理服务器代替“客户端”。
47
How do sensors help in cybersecurity?
They provide real-time traffic data to IDS/IPS for threat detection. ## Footnote 它把实时流量送给 IDS/IPS 检查，用来发现攻击或异常。
48
What is an Application Delivery Controller (ADC)?
An advanced load balancer with security, compression, and optimization features. ## Footnote 增强版负载均衡器，还能加速、加密、防攻击。
49
What’s a key benefit of using a jump server?
It controls and logs admin access, reducing attack surface. ## Footnote 集中控制管理员登录，减少攻击面，还能记录操作。
50
What’s the key takeaway about network appliances?
Each appliance has a unique job—together, they make networks faster, safer, and more manageable. ## Footnote 每个设备都各司其职，组合使用能让网络更快、更安全、更好管理。
51
What is port security?
A switch feature that restricts which devices can connect based on MAC address. ## Footnote 交换机上的一种安全功能，根据 MAC 地址限制谁能接入网络。
52
Why is port security important?
It prevents unauthorized devices from connecting to the internal network. ## Footnote 防止外人插网线就进来，保护内部网络不被随意访问。
53
What does a switch use to identify devices?
MAC address – the unique hardware address of each network device. ## Footnote MAC 地址，每台设备都有唯一编号，交换机靠它来识别。
54
What is sticky MAC?
The switch automatically learns the MAC and locks it to the port. ## Footnote 交换机会自动“记住”第一个接入的 MAC，并把它绑定在端口上。
55
What happens when an unauthorized device connects?
The switch can shut the port, restrict traffic, or just alert (based on config). ## Footnote 交换机会根据设置选择：关掉端口、报警、或只拒绝该设备。
56
What is MAC spoofing?
When a device pretends to use another device’s MAC address to bypass security. ## Footnote 伪装成别人的 MAC 地址，试图混进网络，是一种攻击手段。
57
What is 802.1X used for?
It provides authentication before network access is allowed. ## Footnote 它是一种端口级认证，必须先验证身份才能连接网络。
58
What are the three roles in 802.1X?
Supplicant (user), Authenticator (switch), Authentication Server (RADIUS). ## Footnote 用户端（请求者）、交换机（验证者）、认证服务器（RADIUS）。
59
What is the difference between RADIUS and TACACS+?
RADIUS is faster and works for many platforms; TACACS+ offers more control and is Cisco-specific. ## Footnote RADIUS 快、跨平台；TACACS+ 更细致、更安全，但偏 Cisco。
60
What’s the key takeaway about port security?
It protects the physical entry point of your network—combine it with 802.1X for best results. ## Footnote 它是网络的“第一道门禁”，配合 802.1X 认证效果更强大。
61
What is the purpose of a VPN?
It creates an encrypted tunnel over the internet to keep data safe. ## Footnote 它在公共网络上建立“加密隧道”，让你的数据传输更安全。
62
What is the difference between full tunnel and split tunnel VPN?
Full: all traffic goes through VPN. Split: only work traffic goes through VPN. ## Footnote 全隧道：所有流量都走 VPN；分隧道：只有公司流量走 VPN，其它走本地。
63
What is IPSec used for?
It encrypts and authenticates IP traffic, often used in VPNs. ## Footnote IP 层的加密协议，常用于 VPN，保护数据不被篡改或偷看。
64
What’s the difference between Transport Mode and Tunnel Mode in IPSec?
Transport: encrypts only the data. Tunnel: encrypts entire packet. ## Footnote 传输模式只加密数据部分；隧道模式把整个包都包起来再发，常用于站点对站点。
65
What is ESP in IPSec?
Encapsulating Security Payload – encrypts and authenticates packets. ## Footnote ESP 是用来加密和验证数据包的核心组件。
66
What is TLS used for?
TLS encrypts data at the transport layer (like HTTPS). ## Footnote TLS 是传输层加密协议，比如你打开 https 网站就用了 TLS。
67
What is DTLS and when is it used?
Datagram TLS – like TLS but for UDP, used in video calls or VoIP. ## Footnote UDP 版的 TLS，常用于视频会议、语音聊天等需要速度的应用。
68
What are site-to-site and client-to-site VPNs?
Site-to-site connects two networks; client-to-site connects a user to the office. ## Footnote 站点对站点是公司与公司之间；客户端对站点是个人远程连公司。
69
What does a clientless VPN use?
It uses a web browser (via HTTPS) to access resources—no software needed. ## Footnote 不需要安装软件，用浏览器登录就能访问公司资源。
70
What’s the key takeaway about secure communication?
Encrypt data in transit, choose VPN and protocols based on risk and use case. ## Footnote 数据传输时一定要加密，选对 VPN 模式和协议，才能安全又高效。
71
What is SD-WAN?
Software-Defined Wide Area Network – it manages WAN connections using software. ## Footnote 软件定义广域网，用软件来控制和优化公司各地之间的网络连接。
72
Why do companies use SD-WAN?
To improve performance, flexibility, and security for branch connections. ## Footnote 它让分公司连总部更快、更稳、更安全，还能省网络成本。
73
How is SD-WAN different from traditional WAN?
Traditional WAN is hardware-based; SD-WAN is software-controlled and cloud-friendly. ## Footnote 传统 WAN 靠硬件配置；SD-WAN 全靠软件控制，更适合连接云服务。
74
What is SASE?
Secure Access Service Edge – combines network and security services in the cloud. ## Footnote 安全接入边缘，把网络功能和安全功能放到云端的一体化解决方案。
75
What does SASE include?
It includes VPN, firewall, zero trust access, and cloud security tools. ## Footnote 包含 VPN、防火墙、零信任访问、云访问控制等一整套安全服务。
76
Why is SASE important for modern businesses?
Because users work from anywhere and access cloud apps—it keeps everything secure. ## Footnote 因为员工在任何地方办公、用云服务，SASE 能统一加密、认证、防攻击。
77
What are the benefits of SD-WAN?
It’s cost-effective, boosts app performance, and simplifies WAN management. ## Footnote 省钱、提速、好管理，非常适合有分支机构的公司。
78
Which cloud providers support SASE-like services?
AWS, Azure, and Google Cloud all offer virtual networking and security tools. ## Footnote AWS、Azure、Google Cloud 都有虚拟网络 + 云安全组合服务。
79
Is SD-WAN or SASE better?
They work together—SD-WAN for connection, SASE for security. ## Footnote 它们是搭档，SD-WAN 解决“怎么连”，SASE 负责“连了怎么保护”。
80
What’s the key takeaway about SD-WAN and SASE?
SD-WAN connects branches efficiently, SASE makes those connections secure and cloud-ready. ## Footnote SD-WAN 负责连接各地网络，SASE 让这些连接更安全、更适应云时代。
81
Why is device placement important in network design?
Proper placement ensures fast, secure, and efficient communication. ## Footnote 合理摆放能提高速度、增强安全、防止瓶颈或盲点。
82
What is a screened subnet (DMZ)?
It separates public-facing servers from internal systems to reduce risk. ## Footnote 放网站、邮件等服务的“中间地带”，防止外部攻击波及内网。
83
What is an attack surface?
All the places where an attacker can try to get in. ## Footnote 攻击者可能入侵的所有入口，总之越多越危险。
84
How can we reduce the attack surface?
Disable unused services, restrict access, and close unneeded ports. ## Footnote 关掉没用的服务、端口和权限，做到最小开放。
85
What are common connectivity types?
Wired (stable), Wireless (flexible), VPN (remote access), Cloud links. ## Footnote 有线稳、无线灵、VPN 安全远程、云连接灵活但要加密。
86
What is the difference between active and passive devices?
Active devices can take action (e.g. IPS); passive only monitor (e.g. IDS). ## Footnote 主动设备能“动手”（拦截），被动设备只观察不干预。
87
What does inline vs tap mean?
Inline = traffic must pass through. Tap = monitor copy only. ## Footnote Inline 是“主路”拦截，Tap 是“旁路”偷窥，不会影响流量。
88
What is a fail-open vs fail-closed device?
Fail-open lets traffic through if device fails; fail-closed blocks all. ## Footnote Fail-Open：设备挂了就放行（保可用）；Fail-Closed：挂了就拦（保安全）。
89
When would you choose fail-closed?
When security is more important than uptime, like in banks. ## Footnote 比如银行、政府，宁愿停运也不能让攻击流入。
90
Key takeaway of infrastructure considerations?
Network design must balance performance, risk, and security by placing devices smartly. ## Footnote 设计网络时要合理布置设备，才能在速度、安全和稳定之间找到最佳平衡。
91
What does “least privilege” mean?
Give users only the access they absolutely need—no more. ## Footnote 只给用户完成工作所需的最低权限，越少越安全。
92
What is “defense in depth”?
Use multiple layers of security, so if one fails, others still protect. ## Footnote 像套娃一样多层保护，就算一层失效，还有其它层挡住攻击。
93
What does a risk-based approach mean?
Focus on protecting the most important or vulnerable assets first. ## Footnote 优先保护最容易被攻击、最关键的系统或数据。
94
What is lifecycle management of controls?
Regularly update, review, and retire controls as things change. ## Footnote 控制措施不是一设就完，要定期评估、更新或淘汰。
95
What is the “open design principle”?
Security should be transparent and testable—not based on secrecy. ## Footnote 安全设计应该可以公开验证，而不是靠“藏着掖着”来安全。
96
What’s the first step in selecting controls?
Assess the current state—know your assets, gaps, and risks. ## Footnote 先搞清楚你有什么系统，有什么漏洞，有多大风险。
97
Why is stakeholder involvement important in security planning?
So controls match business needs and get supported. ## Footnote 安全方案得让业务配合，否则再强也推不动。
98
What is benchmarking in security control selection?
Compare with industry standards like NIST or ISO. ## Footnote 对照 NIST、ISO 等标准，看看有没有遗漏或不达标的地方。
99
What types of controls exist?
Technical (firewall), Administrative (policy), Physical (locks). ## Footnote 技术控制（如防火墙）、管理控制（如策略）、物理控制（如门禁）。
100
Key takeaway of selecting infrastructure controls?
Use a structured, risk-aware, and flexible method to choose layered protections. ## Footnote 用有逻辑、懂风险、能调整的方法搭建多层次的安全体系。

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