WHOIS lookup explained: what's actually in a domain registration record
WHOIS is the public directory of who owns a domain. Here's what each field means, why some of them are redacted, and how to read a registration record.
Practical, no-fluff guides for sysadmins and IT pros. Each article ties to a free tool you can use right now.
WHOIS is the public directory of who owns a domain. Here's what each field means, why some of them are redacted, and how to read a registration record.
Just changed an A record and your friend in another country still sees the old site? That's DNS propagation. Here's how to verify when it's actually done — and how long it can take.
An 'open port' isn't a vulnerability by itself — it's information. Here's how to tell whether a port being open is fine, suspicious, or actively dangerous, and what to do about each case.
Every HTTPS site relies on a TLS certificate. Here's how to read one, what each field actually means, and the things that should make you suspicious.
Email spoofing is trivially easy without email authentication. Here's how SPF, DKIM, and DMARC work together — and how to check yours.
Your public IP is the address the rest of the internet uses to talk to you. Here's what it reveals, what it doesn't, and how to check it.
A quick-reference for IPv4 subnet math — how to read a CIDR, what the mask actually means, and the easy way to count usable hosts.
DNS lookups are the first step in almost every network troubleshooting flow. Here's how they work, the record types that matter, and how to run them from your browser.