什麼是防火牆，它如何工作

防火牆是一種網絡安全系統，通過預定義規則監控和控製網絡流量，以保護計算機或網絡免受未經授權的訪問。其核心功能包括：1. 檢查數據包的來源、目標地址、端口和協議；2. 根據信任度判斷是否允許連接；3. 阻止可疑或惡意行為；4. 支持不同類型如包過濾防火牆、狀態檢測防火牆、應用層防火牆和下一代防火牆；5. 用戶可通過操作系統設置啟用內置防火牆，如Windows安全中心或macOS系統偏好設置；6. 防火牆應與其他安全措施如強密碼和更新軟件結合使用以增強防護效果。

A firewall is like a security guard for your network — it decides what traffic gets in and what stays out. Whether you're using one on your home computer or a huge corporate system, its job is simple: protect the system by filtering data based on specific rules.

What Exactly Does a Firewall Do?

At its core, a firewall monitors and controls incoming and outgoing network traffic. It uses predefined rules to determine whether to allow or block certain types of traffic. Think of it as a checkpoint that examines every packet of data trying to pass through.

For example, if someone tries to access your computer from an unknown source, the firewall checks whether that connection request fits within allowed behavior. If not, it blocks it. Firewalls can filter based on IP addresses, ports, protocols, and even specific applications.

Here are some common ways firewalls make decisions:

• Is the source or destination address trusted?
• Is this type of traffic allowed (like HTTP or FTP)?
• Does this connection match a known pattern of malicious behavior?

Types of Firewalls You Might Encounter

Not all firewalls work the same way. Here's a quick breakdown of the most common ones:

Packet-filtering firewalls: These look at basic info like IP addresses and ports. They're fast but not super detailed. Stateful inspection firewalls: More advanced — they track active connections and use that context to make better decisions. Application-layer firewalls: These dig deep into the actual content of the traffic, like checking web requests for suspicious patterns. Next-gen firewalls (NGFW): Combine traditional methods with extra features like intrusion prevention and deep packet inspection.

Most home routers use a basic packet-filtering firewall. Businesses often go for stateful or next-gen versions because they need stronger protection.

How to Set Up a Basic Firewall on Your Computer

You don't have to be tech-savvy to enable a firewall. Most operating systems come with one built-in.

On Windows , you can check your firewall settings through:

• Start menu > Settings > Update & Security > Windows Security > Firewall & network protection Make sure it's turned on for all network profiles (private, public, etc.).

On macOS , go to:

• System Preferences > Security & Privacy > Firewall tab Click the lock to make changes, then turn it on.

Some third-party antivirus tools also include firewall components. Just be careful not to run more than one firewall at a time unless you know what you're doing — they can interfere with each other.

Firewalls aren't foolproof, but they're a solid first line of defense. Combined with good passwords and updated software, they help keep your system safer without much effort.

基本上就這些。

以上是什麼是防火牆，它如何工作的詳細內容。更多資訊請關注PHP中文網其他相關文章！