Outlook & Onedrive downtime is due to hacking, Microsoft confirms

Outlook and Onedrive were affected by an outage earlier this month. Turns out, they were actually hacked.

by Sinziana Mihalache
Sinziana Mihalache
Sinziana Mihalache
Sînziana loves getting people to better understand products, processes, and experiences beyond a simple user guide, either in writing or making use of images. She joined the team... read more
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  • Storm 1359 was identified as the threat actor enabling the attacks.
  • The attacks were coordinated and followed different ways of implementation.
  • No data has been compromised, says Microsoft.
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And the beginning of June, Outlook & Onedrive were down, in what was known then as an internal conflict that provoked the apps to not function.

Well, it turns out, Outlook and Onedrive, as well as other Microsoft hubs and repositories, were the targets of a hacking attack, Microsoft reports.

The threat actor Storm 1359 was identified by Microsoft, as the Redmond-based tech company launched an investigation shortly after the servers were down.

The actor had access to a lot of botnets and tools that allowed it to easily launch DDoS attacks from multiple cloud services and open proxy infrastructures.

Fortunately, no customer data has been accessed or compromised, says Microsoft.

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What is causing the Outlook downtime?

Outlook and hotmail downtime

These DDoS attacks were multiple and different. According to Microsoft, they were done in different ways and their systemic attack was strong enough to bypass Microsoft’s security.

  • HTTP(S) flood attack – This attack aims to exhaust the system resources with a high load of SSL/TLS handshakes and HTTP(S) requests processing. In this case, the attacker sends a high load (in the millions) of HTTP(S) requests that are well distributed across the globe from different source IPs. This causes the application backend to run out of compute resources (CPU and memory).
  • Cache bypass – This attack attempts to bypass the CDN layer and can result in overloading the origin servers. In this case, the attacker sends a series of queries against generated URLs that force the frontend layer to forward all the requests to the origin rather serving from cached contents.
  • Slowloris – This attack is where the client opens a connection to a web server, requests a resource (e.g., an image), and then fails to acknowledge the download (or accepts it slowly). This forces the web server to keep the connection open and the requested resource in memory.  
We’re investigating access and service issues for Outlook. More information will be provided in the admin center under EX512238 as it becomes available.
We’ve begun our targeted restarts to portions of our infrastructure that are impacted by the recent change. We’ll provide more detailed information via EX512238 in the admin center and portal.office.com/servicestatus.

How did it affected the apps?

Problems with essential email functions, such as send, receive, and search, appeared on Outlook.

These are the error messages showing up when users are trying to send emails using the Outlook web service.

It also impacted users of other services, such as Microsoft Teams. Users mentioned that at times they managed to log in, although extremely slow, but then other functionalities of the service remained unresponsive.

How can I access Outlook if the service is down?

1. Use an alternative email client

use an laternative email client

We are recommending Mailbird as a great freeware alternative to Outlook.

This is a simple, extremely reliable email client that lets you manage several email accounts and contacts from a single console.

It’s conveniently integrated with a huge variety of third-party apps such as Google Calendar, WeChat, WhatsApp, Google Docs, Slack. And set up is extremely easy. 



Don't let service outages put off your email activity. Get back in business with this reliable top email client.

2. Use a VPN

bypass outllok downtime with a VPN

Some users mentioned that despite the outage they managed to connect to the Outlook client using a VPN.

We strongly endorse this workaround, considering that a VPN not only protects your online presence but, as seen, can bypass major technical issues given the possibility to access other servers that are functional.

On this note, we recommend PIA (Private Internet Access) because of the huge server database that you can connect to whenever your email client’s servers are down.

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Are you still experiencing problems with the Outlook client? Do try one of the solutions mentioned above and tell us if it helped you get back on track with your emails.

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