Networking & Security Guides
Learn how IP addresses, DNS, email routing, SSL certificates, and network security work. Practical, jargon-free guides for beginners and professionals.
How to Check 301 Redirects and Fix Redirect Chains
What 301, 302, 307 and 308 actually tell browsers and search engines, how to trace a redirect chain hop by hop with curl, and the chain patterns worth fixing.
HTTP Security Headers: What Each One Does and Safe Values to Start With
HSTS, CSP, X-Content-Type-Options, Referrer-Policy, Permissions-Policy and clickjacking protection explained, with safe values to deploy first.
DNSSEC Explained: How to Tell If a Domain Is Signed and Why Validation Fails
How DNSSEC signs DNS answers, what DS, DNSKEY and RRSIG records do, how to check a domain with dig, and the mistakes that turn a signed domain into a SERVFAIL.
Reverse DNS and PTR Records: How They Work and Why Mail Servers Check Them
How IPs map back to hostnames, why only the IP block's owner can set a PTR record, what forward-confirmed reverse DNS is, and how to fix a missing PTR.
Is Your VPN Leaking? WebRTC Leaks, DNS Leaks and What Websites Still See
What a VPN actually hides, how WebRTC and DNS can expose your real IP or ISP anyway, how to test for each leak, and the browser settings that close them.
Why Speed Test Results Vary: Latency, Jitter, Download and Upload Explained
What a browser speed test measures, why results vary between tests, how Wi-Fi and server location affect them, and how to run a test you can trust.
TLS Certificates Are Shrinking to 47 Days: The Timeline and What to Automate Now
CA/Browser Forum ballot SC-081 cut certificate lifetimes to 200 days in March 2026, 100 days in 2027 and 47 days by 2029. The timeline and what to automate.
DMARC Is Now an Internet Standard: What RFC 9989 Changes for Your Record
In May 2026 RFCs 9989, 9990 and 9991 replaced DMARC's RFC 7489. What changed — pct removed, t and np added, the DNS tree walk — and what to update.
Post-Quantum TLS in 2026: Most Browser Traffic Is Already Protected. Is Your Site?
Why browsers adopted hybrid ML-KEM key exchange against harvest-now-decrypt-later, how much traffic uses it in 2026, and how to test a server with openssl.
The Biggest Cloud Outages of 2025–2026, and What Their Post-Mortems Have in Common
AWS, Google Cloud and Cloudflare outages traced to their published root causes: a DNS race, a null pointer, an oversized config file and a BGP withdrawal.
Is It Down or Is It Just Me? How to Diagnose an Outage in Five Minutes
A step-by-step way to tell whether a website or service is down for everyone or only for you, using DNS, ping, traceroute, curl and a few free tools.
AI in Cybersecurity in 2026: What Has Actually Changed for Attackers and Defenders
Separating evidence from hype: documented AI-run attacks, how fast vulnerabilities are now weaponised, where AI helps defenders, and which defences matter most.
AI Crawlers and Scrapers: How to Identify, Verify and Control Them
Which AI bots crawl your site, how much they take versus the traffic they send, how to verify them, and robots.txt rules that separate search from training.
Who Owns a Domain? Reading WHOIS and RDAP Records After GDPR
What a WHOIS or RDAP record can still tell you after privacy redaction, how to read domain status codes, and where to go when the owner is hidden.
MX Records Explained: How Email Routing Works
Understand what MX records are, how they route email, how to check and configure them, and how to troubleshoot common email delivery issues.
How Long Does DNS Propagation Take? TTLs, Caching and a Safe Cutover
Why DNS changes show up in some places before others, how long each kind of change really takes, and the TTL-lowering cutover that avoids downtime.
IP Reputation: What It Is and Why It Matters
Understand IP reputation, how it affects email delivery, website access, and security. Learn how to check and improve your IP reputation score.
DNS Record Types Explained: A, AAAA, CNAME, MX, TXT & More
A complete guide to DNS record types including A, AAAA, CNAME, MX, TXT, NS, SOA, SRV, and PTR records. Learn what each type does and when to use it.
SSL/TLS Certificates: What They Are and Why Your Site Needs One
Learn what SSL/TLS certificates are, how HTTPS works, types of SSL certificates, and how to check and troubleshoot SSL issues for any website.
How to Get Your IP Off a Blacklist: Find the Cause, Then Delist
Which blacklists actually matter, how to find what got your IP listed, and what to send each list to get removed without being relisted.
What Are Ports? Common Port Numbers Every Admin Should Know
Learn what network ports are, how they work, the difference between TCP and UDP, and a reference guide to the most common port numbers used on the internet.
SPF, DKIM, and DMARC Explained: The Email Authentication Trio
Learn how SPF, DKIM, and DMARC work together to authenticate email, prevent spoofing, and improve deliverability. Includes setup examples and troubleshooting.
Why Are My Emails Going to Spam? A Troubleshooting Guide
Diagnose and fix email deliverability issues. Learn the most common reasons emails land in spam and actionable steps to reach the inbox consistently.
What Is Certificate Transparency and Why It Matters
Learn how Certificate Transparency (CT) works, why it was created, how CT logs prevent rogue SSL certificates, and how to monitor certificates for your domain.
How to Check Open Ports with nmap, nc and netstat
Check which ports are listening from inside a machine and which are reachable from outside, with the exact commands and how to read open, closed and filtered.