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secure-os wrote

SSH Permission denied (publickey): the Server Is Not Refusing Your Key, It Never Saw One

Sep 6, 2026 in ssh, authentication, linux - The message says publickey, so people regenerate keys. That is almost never the problem. In descending order of frequency: the wrong key was offered, the file permissions are too open, the username is wrong, or the server does not allow that method. How to find out in one command.

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📅 4 min read🛡️ Threat-model-first

secure-os wrote

How to Stop Robocalls: What Works, What Only Feels Like It Works

Sep 6, 2026 in phone, scams, privacy - Blocking numbers one by one cannot keep up with software that changes number every call. What actually reduces the volume is carrier filtering, a setting already on your phone, and one habit that costs nothing. Also: why answering at all makes it worse.

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📅 4 min read🛡️ Threat-model-first

secure-os wrote

Your Phone Has Been Stolen: the First Hour, in Order

Sep 6, 2026 in phone, theft, accounts - Locating it is not the first thing to do, and it is rarely the useful one. What matters in the first hour is the accounts the phone was signed into and the SIM that receives your codes. The order that limits the damage, and the two steps to take before it ever happens.

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📅 4 min read🛡️ Threat-model-first

secure-os wrote

Linux Audit Log Commands: the Six That Answer Real Questions

Sep 5, 2026 in linux, logging, auditd - journalctl, ausearch, aureport, last, lastb and auditctl cover almost everything you will ever need to ask a Linux system about its own past. What each one sees, what none of them see, and why a log on the machine is evidence of a different quality than a log shipped off it.

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📅 4 min read🛡️ Threat-model-first

Operating systems

Qubes, Tails & Whonix

Which secure OS fits which threat model - compartmentalisation vs amnesic vs Tor-routed.

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Encryption

Full disk encryption

LUKS, BitLocker, FileVault and VeraCrypt - what each protects, and what it does not.

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Hardening

Threat-model-first Linux

Practical hardening built around the adversary you actually face.

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