Large-scale DDoS attacks disrupted Threema secure messaging service

Multiple distributed denial-of-service (DDoS) attacks targeted the Threema secure messaging service earlier this week, causing severe disruptions to communications.

​Organizations using Threema On-Prem did not experience any issues because they rely on their own infrastructure.

In a post-mortem report on Friday, the end-to-end encrypted instant messaging service said that the attacks were difficult to defend against because the threat actor constantly changed patterns.

Threema is a paid messaging application developed by the Swiss technology company of the same name, with a heavy focus on security and privacy.

The service relies on its own server infrastructure in various locations in Switzerland and promises “no ads, no profiling, no hidden data analyses.”

On Tuesday around 6 PM UTC, users started to report service interruptions. The company responded about an hour later, saying that based on the information available at the time, the cause was “a network outage on our colocation partner’s side.”