# Knowledge base — security writing from practice | RootCore LLC

> How a card testing attack runs, why your mail does not arrive without DMARC, and what to do in the first hour after a break-in.

Page: https://cyber-security.rootcr.com/en/knowledge/
Updated: 2026-08-20

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# Knowledge base

> **In short:** These are write-ups that answer one concrete question end to end: what happens during an attack, what can be done about it, and which setting actually matters. Not general security advice — this is what we tend to write down for a client after an incident or an audit. Each piece stands on its own, and each is usable even if you never hire us.

If there is a question you cannot find an answer to, write to us: the next pieces come from the questions we get asked most.