Mullvad Public DNS Shuts Down Nov 2: 5 Checks I Ran First
On September 3, Mullvad announced it is shutting down the public encrypted DNS servers it has run since 2022 and sponsoring Quad9 instead. If you ne…
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I Traced Unbound's DNSSEC Heap Overflow: 4 Checks to Run
[ attacker's zone ] ──► ┌────────────────────────────┐ │ Unbound (recursive, DNSSEC)│ │ CVE-2026-81642 CWE-122 │ │ DNSKEY -> digest buffer │ └───…
cert-manager-webhook-freens: сертификаты Let's Encrypt на все поддомены в Kubernetes через бесплатный российский DNS
Казалось бы, что там может быть интересного — A-запись прописал и забыл. Ан нет: стоило захотеть один сертификат сразу на все тестовые поддомены и п…
DoH JSON from the browser: 5 ways Cloudflare and Google differ
Two public resolvers answer DNS queries over HTTPS in JSON: Cloudflare at https://cloudflare-dns.com/dns-query and Google at https://dns.google/reso…
I sampled 330 IPs from 11 VPS providers. Reverse DNS ranged from 0% to 100%, and the blocklist number needs unpacking.
After my last post on cloud provider IP ranges, a few people asked the obvious follow-up: what about the VPS companies you actually buy from? Fair.…
Setting Up DNS for SaaS Emails
When you create a Software as a Service (SaaS) or a social web platform, one of the often-overlooked parts of it is the email DNS configuration. I l…
Logistics Hostname Broke After Adding an Alias (DNS Cutover Constraint)
Short answer: restore the hostname by removing the newly introduced CNAME or the other data at the same owner name, then wait for authoritative answ…
DNS Zone Erasure: Automated Pipeline Decisions from Deliverability Evidence
Put an evidence gate in front of every zone teardown, and make that gate bind the tenant, exact zone identifier, observed mail state, and approval t…
Go Reconciliation of Intended and Current DNS Configuration State
Short answer: treat DNS as a control loop, not a sequence of successful API calls. For a fintech platform that gives every tenant a subdomain, the i…
Game Tenant DNS Cutover — Pre-change TTL Scheduling and Auditable Restore
A tenant subdomain cannot move faster than the cached answer already held by resolvers. For a gaming platform that assigns one subdomain to every te…
Domain Retirement Guard: Log Intent Before a Destructive Automation Operation
An e-commerce migration changes the answer when one automation account can see both customer-owned and platform-owned zones. Short answer: permit de…
Customer Support DNS: Migrate a Zone with 4-Gate Diff Before Nameservers
The page arrives after a customer changes nameservers: their support portal passes ownership checks, but mail for the same domain no longer behaves…
DNS Record Write Rejected Because Zone ID Is Not Domain Name — Validation Debug
Short answer: when a DNS record write is rejected because a zone ID is not a domain name, resolve the opaque reference first, canonicalize the retur…
Property Domain Offboarding — Delete Records Without Whole-Zone Risk
Short answer: retire only the records owned by the departing property, never the whole DNS zone, unless an ownership check proves that the zone itse…
4 Failure Modes of TXT Record Domain Ownership Verification in FastAPI Onboarding
Before writing any verification code, settle one thing about the customer's DNS: does your platform hold the zone, or does the customer? For a devel…
Mail Going to Spam After Setup in 2026: Debug SPF, DKIM, DMARC Alignment
Short answer: inspect one received message and find which authenticated domain aligns with the visible From domain; DMARC passes when an aligned SPF…
ISC BIND 9.18.42 Released: Major Milestone for DNS Security
ISC BIND 9.18.42 Released: Major Milestone for DNS Security Meta: ISC’s BIND 9.18.42 hit the open‑source stage on November 5, 2025, delivering a sui…
Pushgateway Heartbeat Gotcha: When ndots and NetworkPolicy Silently Eat Your Alerts
A CronJob exits 0, Pushgateway shows a heartbeat metric that hasn't updated in days, and Prometheus fires nothing. Every dashboard is green while th…
Debugging VPN DNS Problems: Find the Layer That Is Actually Answering
When DNS starts behaving strangely—a site resolves differently than expected, a recent change does not appear, or two devices disagree—the VPN often…
DNS Records Explained: A, AAAA, CNAME, MX, TXT, NS, and SRV Records in Modern Internet Infrastructure
In the previous article , we explored how DNS translates human-friendly domain names into machine-friendly IP addresses and how a request travels th…
Как показать клиенту новый сервер до переключения DNS
Изначально я пилил инструмент совершенно под другие задачи - закрывать админки и внутренние сервисы от ботов и посторонних глаз. Но в процессе работ…
How to Check SPF, DKIM, and DMARC Records in Python
If your app sends email — transactional or marketing — three DNS records decide whether it lands in the inbox or the spam folder: SPF , DKIM , and D…
DNS Round-Robin: The Cheapest Load Balancer Is Three A Records and a Rotating Answer
Originally published at https://blog.pathvector.dev/protocol-lab-dnsrr-41/ — part of the free Protocol Lab series. This post is part of Protocol Lab…
Building a Lightweight DNS Exploration Tool in Python
When building out network enumeration tooling, understanding how domain structures map out is a core skill for any security enthusiast or developer.…
DNS Propagation Time: How Long Until Your DNS Change Goes Live?
You change the A record for api.example.com from 203.0.113.10 to 203.0.113.20`. Your browser shows the new IP. The deployment dashboard says green.…
А мой веб-сервер точно нормально работает?
У меня есть сервер в интернете, который работает с HTTP/2, HTTP/3, с IPv4 и IPv6… Как всё это хозяйство протестировать? Я не нашёл решение и прибёг…
97.8% of the top 10,000 domains have no MTA-STS. Here's how to be in the other 2%
Of the 10,000 most-visited domains on the web, 97.8% have no MTA-STS policy at all. Not misconfigured. Not weak. Just absent. I scanned the Tranco t…
DNS Explained: How Your Browser Decodes Website Addresses
You type www.google.com into your browser and hit Enter. The page loads in under a second. But stop and think about what just happened. Your browser…
Wildcard DNS Records: Uses, Risks, and Best Practices
A single DNS record can answer for an unlimited number of subdomains. Add one wildcard entry, and suddenly anything.yourcompany.com , literally-anyt…
Foghorn : a blunt non-DNS solution
What ? Foghorn is a sender/listener pair that periodically sends UDP packets to a destination/subnet , and listens for any other utilities sending s…