Sorry we shut you out, says Tutanota: Encrypted email service weathers latest of ongoing DDoS storms

Privacy-conscious biz insists on rolling its own mitigations, though

Encrypted email biz Tutanota has apologised for accidentally shutting its own users out while fending off the latest of a series of distributed denial-of-service (DDoS) attacks.

Tutanota has been forced to defend against the assaults since August, with the service experiencing various levels of downtime as a result.

"It is a challenge to protect a privacy-focused service such as Tutanota from DDoS attacks because we need to block high-level application attacks ourselves," co-founder Matthias Pfau told The Register.

Attacks publicly acknowledged on Twitter by Tutanota took place on 27 August as well as the 6th, 7th, 10th and 13th of September.

In a statement published this morning, the encrypted email provider said: "While we were able to mitigate most of the [latest] DDoS, an overreacting IP-block to fight the attacks led to hundreds of users not being able to access Tutanota for multiple hours this Sunday. We deeply apologize for this mistake; it has now been fixed."

German DDoS mitigation service Link11 is being used by Tutanota to block low-level "volume" attacks, while high-level attacks continue to cause behind-the-scenes head-scratching. Pfau highlighted, in the latest Tutanota blog post about the ongoing attacks, that turnkey DDoS mitigation services would require access to Tutanota's SSL certificates, something the firm is not willing to do.

The most recent attack temporarily stopped service yesterday (13 September), triggering the usual wave of irritated tweets from users wondering what was going on:

We are tweaking our algorithms against the attackers so this can happen to some. Please send this info to [e-mail] :
How are you accessing Tutanota (Home-IP, VPN)?
What is your public ip (ipv4 and ipv6 - verify https://t.co/18LNJdgt4E)
Which URL didn't work?

— Tutanota (@TutanotaTeam) September 13, 2020

Reg reader Chris was particularly unhappy. "What [the attackers] are doing is actually working – I rely on Tutanota for both business and personal email, and if this continues, then I will have to reluctantly leave them. This is probably what the DDoSers want. Which pisses me off, to be honest. I don't want to be here on Gmail."

A status page, found at https://status.tutanota.com, now tells users whether Tutanota is down or not.

This is a change from last week when Tutanota simply didn't have a status page at all and refused to use one hosted by an external provider such as Google. Co-founder Pfau told The Register: "We can't use a Google service because people checking our status page would then be tracked by Google, which defies our privacy goals. That's also why we don't use any Google services in the Tutanota application, e.g. we handle push notifications on Android ourselves and we've also built our own captcha (instead of using Google's reCaptcha)."

Earlier this year Tutanota was blocked in Russia after irritating the authorities there once too often, shortly after AT&T, an American telco, seemingly spent a fortnight intermittently blocking access to Tutanota's encrypted mailboxes. ®