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ProtonMail hit by mystery DDoS attack, preventing customers from accessing their secure email

End-to-end encrypted email service ProtonMail is suffering from an “extremely powerful” distributed denial-of-service attack, that has knocked it offline, and stopped users from accessing their inboxes.

Switzerland-based ProtonMail has its fair share of fans amongst those who wish to keep their communications secret and secure, as its architecture is designed to never give ProtonMail any method of decrypting your messages, even if they were to receive demands from law enforcement agencies – but clearly the DDoS attack shows that not everyone is a fan.


In a blog post, ProtonMail explains that the attack began on Tuesday November 3rd, firstly flooding its IP addresses and then targeting the Swiss data centre where it houses its servers. According to the firm, the websites of several other tech companies and even some banks were also disrupted as a result of the internet attack.

Although ProtonMail says that it is working hard to restore normal operations, at the time of writing the ProtonMail site remains offline.


On its website (when it’s online) ProtonMail boasts about the security of its data centre:

“Our primary data centre is located under 1,000 meters of granite rock in a heavily guarded bunker which can survive a nuclear attack.”

But such physical security is no barrier for hackers hell-bent on launching a denial-of-service attack. Customers who are affected are advised to follow ProtonMail’s Twitter account for updates.

One of the most frequent security models you will hear about is the CIA triad: Confidentiality, Integrity and Availability.

In many people’s eyes ProtonMail scores well on confidentiality and integrity, but with it being struck so hard by the DDoS attack it is failing at the moment when it comes to availability.

After all, what use is a secure email service if you can’t access your emails?

Fortunately, a denial-of-service attack may prevent users from reaching their inboxes, but it wouldn’t in itself indicate a breach of ProtonMail’s security or that hackers have been able to access users’ messages.

We hope that ProtonMail, who are – we shouldn’t forget – the victims of a criminal attack, are able to restore their systems to normal operation sooner rather than later.

In the meantime, however, it seems that a legitimate question to ask is this:

Who on earth would be keen to disrupt access to a secure email service, and potentially put it out of business?

Leave your opinion and conspiracy theories as a comment below…

About the author


Graham Cluley is an award-winning security blogger, researcher and public speaker. He has been working in the computer security industry since the early 1990s, having been employed by companies such as Sophos, McAfee and Dr Solomon's. He has given talks about computer security for some of the world's largest companies, worked with law enforcement agencies on investigations into hacking groups, and regularly appears on TV and radio explaining computer security threats.

Graham Cluley was inducted into the InfoSecurity Europe Hall of Fame in 2011, and was given an honorary mention in the "10 Greatest Britons in IT History" for his contribution as a leading authority in internet security.


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  • ummm…

    maybe any one of the many shady security services from one of the many shady western powers?

    it has to be!

    disgusting behavior…. however it is all too commonplace these days

  • So, if I understand correctly, one or a few secure locations (and/or finite set of IPs), is the potential downfall of such services, since they cannot replicate on a network of servers outside their own predetermined “domain” like a cloud can? If so, there has to be a better solution. Otherwise any party with control of many PCs could disrupt service. This could include hackers, virus makers and government bodies and maybe the 15-year-old kid down the street. Someone should be marketing a scrubber layer and or access and login system that separates the already signed-up users from general internet traffic. That way the hackers would have to have credentials in order to move traffic onto the dedicated/working IPs.

  • Love your work Graham..

    So heres the thing..
    PROTONMAIL DDoS story.


    Andy Yen alledges, in his blog that the characteristics of the pre-ransom “criminal”attack and the second post Ransom attack were APPARENTLY quite different. The second showing a very different level of sophistication and resources, and different target vectors.
    Today a further attack has been mounted.

    Ask yourself three questions.

    1. Que Bono? Who is Protonmail (a meagerly resourced startup) a legitimate target for? A bunch of eastern European/russian crooks? To extort $6000? fOR POCKETMONEY?
    Risk reward is ridiculous. Or another more serious player?

    2. why would the same bunch of crooks who launched the initial attack then, having already been paid, IMMEDIATLY launch a further much more highly sophisticated structural attack, with many of the characteristics of a state-RESOURCED-player?
    …and then mail a denial of their responsibility of the second? ???

    3. Why did the second attack target Protonmails upstream infrastructure, an area of great sensitivity to the Swiss and one designed to create problems for the continued hosting of the Protonmail end to end encryption service model? And attract significant investigative resources from Swiss national and European cybercrime resources. wHAT ? FOR ANOTHER $6000? Risk-Reward doesnt stack up. No Way.

    One bizarre scenario.. would be that the first (criminal) attack was a sponsored diversion, and the second, the real attack, launched by a state player with the much more credible and clearer objective to take Protonmail off line permanently because their Swiss based endtoend encryption model was proving a problem to hack.
    Not a story that would implicate, for example, a State Player?

    And masking the real play.

    Impossibly far fetched of course.


  • Not clear whether ProtonMail hosts Neomailbox but this was down over the weekend, along with Norwegian service Runbox. All secure mail services… Hmmm.