Merge pull request #467 from 8go/patch-98

node_operations: minor additions to security

node_operations.asciidoc

@@ -464,7 +464,7 @@ Once done reconfiguring, repeat the port check using one of the websites from th
 
 === Security of your node
 
-A Lightning node is, by definition, a hot-wallet. That means that the funds (both on-chain and off-chain) controlled by a Lightning node are directly controlled by keys that are loaded in the node's memory. If a Lightning node is compromised, it is trivial to create on-chain or off-chain transactions to drain its funds. It is therefore critically important that you protect it from unauthorized access.
+A Lightning node is, by definition, a hot-wallet. That means that the funds (both on-chain and off-chain) controlled by a Lightning node are directly controlled by keys that are loaded in the node's memory or stored on the node's hard disk. If a Lightning node is compromised, it is trivial to create on-chain or off-chain transactions to drain its funds. It is therefore critically important that you protect it from unauthorized access.
 
 Security is a holistic effort, meaning that you have to secure every layer of a system. As the saying goes: the chain is only as strong as the weakest link. This is an important concept in information security and we will apply it to our node.
 
@@ -477,17 +477,18 @@ Securing an operating system is a vast topic that is beyond the scope of this bo
 
 To secure your operating system, here are some of the top items to consider:
 
-. Provenance - Start by ensuring that you are downloading the correct operating system image and verify any signatures or checksums before installing it.
+. Provenance - Start by ensuring that you are downloading the correct operating system image and verify any signatures or checksums before installing it. Extend this to any software that you install. Double-check any source or URL from where you download. Verify the integrity and correctness of the downloaded software via signature and checksum verification.
 . Maintenance - Make sure that you keep your operating system up to date. Enable automated daily or weekly installation of security updates.
 . Least Privilege - Set up users for specific processes and give them the least access needed to run a service. Do not run processes with admin privileges (e.g. root).
 . Process Isolation - Use the operating system features to isolate processes from each other.
 . File System Permissions - Configure the file system carefully, on the least-privilege principle. Do not make files readable or writeable by everyone.
-. Strong Authentication - Use strong randomly generated passwords, or whenever possible public-key authentication e.g. with Secure Shell (SSH) instead of passwords.
-. Two-factor Authentication (2FA) - Use two-factor authentication wherever possible, including Universal 2-Factor (U2F) with hardware security keys.
-. Backup - Make backups of your system, but make sure you protect the backups with encryption too.
+. Strong Authentication - Use strong randomly generated passwords or, whenever possible, public-key authentication. E.g. it is safer to use Secure Shell (SSH) with a cryptographic key pair instead of a password.
+. Two-factor Authentication (2FA) - Use two-factor authentication wherever possible, including Universal 2-Factor (U2F) with hardware security keys. This applies to all external services you might be using such as your cloud service provider. But you can apply this also to your own set-up such as your own SSH configuration. Use 2FA also for indirect services. Say you are using a cloud service. You gave your cloud service provider an email address. Also protect your email address with 2FA.
+. Backup - Make backups of your system, but make sure you protect the backups with encryption too. Perform these backups periodically. At least once test if you can restore your backup and that your backup is complete and accessible. If possible, keep one copy of your backups on a different disk to avoid that a single hard disk failure destroys _both_ your active node as well as your backup copies. 
 . Vulnerability & Exposure Management - Use remote scanning to ensure you have minimized the attack surface of your system. Close any unnecessary services or ports.
+- Minimize - Install only software and packages that you really need and use. Uninstall packages that you no longer use. It is recommended that you do _not_ use your node computer for non-node activities that you can perform on another of your computers. Especially, if you can, do _not_ use your node computer for browsing, surfing the internet, or reading your email.
 
-This is a list of basic security measures, not an exhaustive list.
+This is a list of the most basic security measures. It is by no means exhaustive.
 
 ==== Node Access