> For the complete documentation index, see [llms.txt](https://huang-jason.gitbook.io/web-general/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://huang-jason.gitbook.io/web-general/security.md).

# Security - SSH/firewall/VPN

## 1. SSH Keys

* **private key** is kept secret and **secure by the user**
* **public key** can be shared with anyone.
* Password - you can try to get correct one.
* SSH - have many more bits of data, and it is harder to guess.

![](/files/-Lq83V28g-Ias5XMRs2l)

## 2. Firewalls

![](/files/-Lq83V2AXczEFQgy_dmu)

## VPNs and Private Networking

![](/files/-Lq83V2Cnz25fOtpmhln)

<https://www.digitalocean.com/community/tutorials/how-to-secure-traffic-between-vps-using-openvpn>

## 3. Public Key Infrastructure and SSL/TLS Encryption

Prevent **man-in-the-middle** attacks

![](/files/-Lq83V2Ews2_T74CIZpN)

## 4. Service Auditing

discovering what services are running on the servers in your infrastructure.

```
sudo netstat -plunt
```

Stay attention to are `Proto`, `Local Address`, and `PID/Program name`.

If the address is `0.0.0.0`, then the service is accepting connections on all interfaces.

![](/files/-Lq83V2GtyCQHCt-qQag)

## 5. File Auditing and Intrusion Detection Systems(IDS)

File auditing = detect changes to the system that may have been authorized.

IDS monitors a system or network for **unauthorized activity**.

<https://www.digitalocean.com/community/tutorials/how-to-use-tripwire-to-detect-server-intrusions-on-an-ubuntu-vps>

<https://www.digitalocean.com/community/tutorials/how-to-install-aide-on-a-digitalocean-vps>

## 6. Isolated Execution Environments

Separating your components can limit the access that an intruder has to other pieces of your infrastructure.\
![](/files/-Lq83V2IVbw8emPC4SBp)


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