Why a VPN Can Work Today and Fail Tomorrow
A tunnel that worked yesterday can stop working with no change on your side. The documented record shows four distinct causes, and only one of them is the censor.
A VPN that connected cleanly last month can refuse to connect this morning, and the software on both ends can be byte-for-byte identical. That experience is usually read as a verdict on the tool. It is better read as a report about the environment, because the environment is the thing that changed.
What internet censorship is already states the mechanism in a single line: a tool can work for months and then stop working with no change to the tool, because something moved down the stack. This article is the evidence behind that line, and a taxonomy of the four distinct ways it happens.
Short answer#
Four mechanisms account for almost every documented failure of a working VPN in the last five years. They are worth separating because they call for different responses.
- The censor learns a signature. Detection precedes blocking, and the identification is the durable half of the operation.
- The censor escalates between levers. Addresses, protocols, hosting subnets and app distribution are separate levers, and the record shows them pulled in sequence.
- The censor applies a block unevenly, or takes it back. Mobile and fixed networks behave differently, regions differ from one another, and a national filter has finite capacity.
- Somebody other than the censor moves. Cloud providers, app stores and payment processors have removed circumvention capability through ordinary business decisions, with no government order involved at all.
Only the first is what most people picture when they think of a VPN being blocked. The other three appear at least as often in the record, and the fourth is not censorship.
Detection comes first, and it lasts#
Nothing is blocked before it is identified, and identification is the part that does not get rolled back. A block can be lifted; a signature, once published or once learned by a classifier, sits in the system permanently.
Roskomsvoboda’s study of Russian circumvention cites a 2022 CensoredPlanet experiment that identified 85% of traffic going through OpenVPN. The study behind that number is worth reading for its framing rather than its figure: the classifier was trained on flows from an ordinary internet provider position, using byte patterns, packet sizes and server behaviour, which are all properties a client cannot stop having.
The same asymmetry shows up in the obfuscated case. Commercial VPNs sold as OpenVPN-with-a-wrapper were fingerprinted at scale, and the authors found that most implementations resembled plain OpenVPN with a simple transformation applied. That detail matters for the escalation story below, because it means the censor does not need to break encryption or mount an active attack. It needs one stable observable, and stability is exactly what a widely deployed client provides.
Escalation between levers#
Russia’s last five years are the best-documented case of a censor working through a list of levers rather than finding one decisive move.
The chronology, drawn from Roskomsvoboda’s report and contemporaneous trade press:
- June 2021. VyprVPN and Opera VPN blocked by name.
- September 2021. Hola, ExpressVPN, KeepSolid VPN Unlimited, NordVPN, Speedify and IPVanish blocked by name. In the same month, users on Rostelecom and Beeline mobile networks began reporting WireGuard connection failures, which Roskomsvoboda reads as an early TSPU attempt that also caught Avito, Twitch and other unrelated services.
- 23 January 2023. In the eastern regions, IKEv2 and OpenVPN protocols were blocked, while the IP addresses of the VPN servers themselves remained available.
- 30 May 2023. Partial blocking of OpenVPN, IKEv2 and IPSec.
- August 2023. OpenVPN and WireGuard clients stopped working, reported primarily by users of Beeline, Megafon, MTS, Tele2, Tinkoff and Yota. Traffic on landline and business connections largely kept flowing. At least 6 of 15 popular services lost access.
- December 2025. TSPU settings updated; SOCKS5, VLESS and L2TP placed under active disruption.
- February 2026. Roskomnadzor reported 469 circumvention services blocked, up from 439 in January and 258 in October 2025.
Three things in that list deserve more attention than the dates themselves.
The January 2023 entry is the cleanest natural experiment in the public record. The protocol was blocked and the server address was still reachable. Those are two different layers of the censorship stack, and an operator who can act on one is not thereby able to act on the other. It also means the failure a user experiences is not diagnostic on its own: a connection refused for protocol reasons and a connection refused for address reasons look identical from the client.
The August 2023 entry shows the same escalation pattern from the other side. The block was real, and it was partial. It applied mainly to mobile networks, which is where the volume of ordinary residential traffic sits, while business and landline accounts carried on. That distinction is not a technical curiosity. It is the difference between a policy that targets the general population and one that spares foreign companies still operating in the country.
The 2025 and 2026 entries show that the escalation did not stop at protocols. Human Rights Watch reported in September 2026 that the recent waves targeted VPN services’ infrastructure directly: large blocks of IP addresses, including entire subnets allocated by their hosting providers. One affected service told the organisation that restoring access after bulk subnet blocking takes longer and costs more than the earlier, more granular address blocking. When a censor moves from blocking an address to blocking the range an address lives in, the cost of being a tenant on somebody else’s network goes up sharply.
Blocking is applied unevenly and can be reversed#
A national filtering system is a physical installation with finite throughput, and it does not behave like a logical switch.
Roskomsvoboda’s study notes that Russian TSPU blocks are enforced differently per region, which ValdikSS attributed to local filtering capability rather than to any announced policy. The August 2023 OpenVPN and WireGuard failures followed the same shape: mobile operators in the lead, fixed lines largely untouched, and access restored on 8 August 2023 after roughly a week.
The capacity limit is documented too. Mediazona reported in April 2026 that a source in the telecoms market described current TSPU infrastructure as not always coping with traffic volume, with the practical consequence that blocked resources occasionally became accessible. The same reporting described a Ministry of Digital Development plan to expand TSPU capacity two-and-a-half times by 2030.
Iran provides the measurement complement to the Russian case reports. The IRBlock study, presented at USENIX Security 2025, measured the whole of Iran’s IP address space over 2.5 months and tested more than 500 million apex domains. It recorded 6.8 million addresses subject to DNS poisoning and HTTP blockpage injection, 5.4 million subject to UDP disruption, and over 6 million censored fully qualified domain names. It also found that blanket blocking of entire top-level domains caused large collateral damage to innocuous websites, which is the same failure mode Roskomsvoboda observed in Russia in September 2021 when Avito and Twitch went down alongside the intended targets.
The pattern generalises: a filter that is aggressive enough to catch a target is usually aggressive enough to catch neighbours, and the neighbours are politically expensive.
When the censor steps back#
The clearest documented reversal is the August 2023 restoration. Roskomsvoboda records that access to the blocked protocols was restored on 8 August 2023, and that on the evening of that day the availability of all services was restored. The same report notes that VPN connections from abroad into Russia continued to work throughout, which reads as a deliberate carve-out rather than a gap.
A subtler form of stepping back is the VLESS episode. In late 2025, reports circulated that Roskomnadzor had blocked VLESS, one of the more advanced circumvention protocols. Mediazona’s April 2026 account is more careful with that claim, and its caution is the instructive part: the reality was more nuanced, and most VPN providers responded by issuing new configurations to their users. Disruption is not removal. A protocol can be degraded enough that every existing client configuration stops working, while the protocol itself continues to function once the parameters change.
That distinction is why “is VLESS blocked in Russia” is the wrong question. The right question is what the block looks like, how long it takes to work around, and what the workaround costs.
Somebody other than the censor moves#
This is the section most coverage of VPN blocking omits, and it is the one with the strangest failure record.
Domain fronting is the case study. The technique, formalised in a 2015 paper by Fifield and colleagues, made a request to a blocked service indistinguishable from a request to a popular CDN-hosted domain, because the censor could see the outer name but not the inner one. The Signal Foundation described the censor’s dilemma plainly: to block one domain-fronted site you have to block the rest of the internet as well.
It worked for years. Then the providers closed it, one after another, on their own schedule:
- Cloudflare had disabled domain fronting since 2015.
- On 14 April 2018, Google blocked it in its cloud.
- On 27 April 2018, Amazon announced it was blocking it.
- In March 2021, Microsoft announced an intention to ban it in Azure.
None of those decisions was a censorship order. They were policy changes by companies that did not want their infrastructure used as a front, and they removed a capability that circumvention tools had depended on. Tor’s response was to move its domain-fronting traffic to Azure, and a Tor spokesperson told CyberScoop at the time that the project had moved all of its domain-fronting to run there.
The Russian case supplies the other half of the story, and it is the half that connects to the provider layer. When Telegram was blocked in April 2018, Roskomnadzor blacklisted millions of IP addresses belonging to Google and Amazon CDN infrastructure. Mediazona’s account of that episode notes that Hetzner space was caught in the same sweep, and that the effort was eventually abandoned. Psiphon’s Michael Hull, asked about the technique at the time, told CyberScoop that domain fronting on its own is not very effective, that it has to be combined with obfuscation, HTTP header modification and transport fragmentation to defeat a sophisticated censor, and that the importance of a diversified circumvention toolbox cannot be overstated. He also observed that the technique breaks the CDN design, which is a concise explanation of why the CDNs stopped tolerating it.
Two more vectors from the same period complete the picture. Apple removed 468 utility applications, a category that includes VPN clients, from its Russian App Store in 2025, and by early 2026 the company had removed several named VPN apps on Roskomnadzor’s demand. In March 2026, Russia’s four largest mobile operators were ordered to stop allowing Apple account top-ups from mobile phone billing, which removed a common way of paying for those apps. Neither of these is network filtering. Both are effective.
What the pattern implies#
If reachability is a property of the environment, then asking whether a VPN is blocked is the wrong unit of analysis. Four questions are better:
- Which layer is being acted on right now? Address, protocol, provider subnet, app distribution and payment are all different layers with different remedies.
- Is the block total, partial or reversible? The record contains all three, often for the same protocol in the same month.
- Who else could move? A capability that depends on a cloud provider’s terms of service has a different failure schedule from one that depends on a censor’s budget.
- What is the recovery path, and what does it cost? Bulk subnet blocking is explicitly described as slower and more expensive to recover from than address-level blocking, and that cost lands on the operator rather than the user.
Obfuscation and encryption answer the detection question, and they answer it well. What they do not answer is which addresses the operator has left, which subnets those addresses sit in, whether the app store still distributes the client, or whether the payment rail still works. Those are infrastructure questions, and they are covered separately in who controls the infrastructure.
Those questions are the job description of whoever runs the network, and they are answered by practice rather than by a feature. Maronix treats reachability as ongoing work: the team researches detection methods, including DPI, and blocking techniques as they appear, provisions and replaces nodes as subnets get caught in bulk blocks, and tracks how networks in restricted places behave from one week to the next. A tool configured once and left alone eventually meets a censor that has moved. An operator still working the four layers above usually moves first.
Common misconceptions#
“If my VPN works, it is working.” It is working at this moment, on this network, at this layer. The August 2023 Russian block was real for mobile users and absent for landline users on the same days.
“A blocked protocol is a dead protocol.” VLESS was reported as blocked in late 2025 and most providers responded by shipping new configurations. Degradation and removal are different events.
“Blocking is permanent.” Access to OpenVPN and WireGuard in Russia was restored on 8 August 2023 after roughly a week of disruption. Restoration is documented, not hypothetical.
“Encryption is what fails.” No cipher in this record was broken. Every failure above was a failure of reachability, classification or distribution, which are properties of the network and the supply chain rather than of the cryptography.
“It is always the censor.” Google, Amazon, Microsoft, Apple and Cloudflare have all removed circumvention capability or distribution through ordinary business decisions. The failure schedule of a technique can be set by a terms-of-service update.
Related#
- What Is Internet Censorship? — the five-layer model this article’s chronology is read against
- What Is Deep Packet Inspection? — the layer that produces the signatures detection depends on
- Obfuscation vs Encryption — what each one can and cannot answer about the detection problem
- What Is WireGuard? — a protocol whose wire appearance is itself the signature
- Who Controls the Infrastructure? — the layer where provider decisions become reachability decisions
- What Makes a VPN Resistant to Censorship? — the six-layer stack these failures are measured against
- What Is Maronix? — the service whose answer to these four questions is an ongoing practice
Sources
- VPN in Russia: from blocking services to blocking protocols Roskomsvoboda
- Russia blocks OpenVPN and WireGuard VPN protocols Risky Business Media
- IRBlock: A Large-Scale Measurement Study of the Great Firewall of Iran (USENIX Security 2025) USENIX
- Behind the curtain: Russia's internet censorship in 2026 Mediazona
- Russia Crackdown on Bypassing Online Censorship Human Rights Watch
- Domain fronting has a dwindling future CyberScoop
- Domain fronting Wikipedia
- Snowflake, a censorship circumvention system using temporary WebRTC proxies (USENIX Security 2024) USENIX
Last reviewed October 22, 2026. Corrections and additions are welcome.