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Large-Scale DDoS Attacks Disrupt Threema Messaging Service

Large-Scale DDoS Attacks Disrupt Threema Messaging Service

First seen 17 Aug 2026, 00:46 UTC • •

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ThreatCluster AI
ThreatCluster •August 17, 2026 at 22:48 UTC
  • •Threema faced multiple large-scale DDoS attacks causing severe service disruptions.
  • •Users in Switzerland, India, and China reported significant outages starting August 15, 2026.
  • •Organizations using Threema On-Prem were not affected due to their independent infrastructure.

Threema, a secure messaging service, experienced significant disruptions due to multiple large-scale DDoS attacks earlier this week. Users reported outages starting on August 15, 2026, particularly affecting those in Switzerland, India, and China. Organizations using Threema On-Prem were unaffected as they operate on their own infrastructure. The attacks were characterized by a constantly changing pattern, making them difficult to mitigate. Threema confirmed that both its service and its colocation partner, Nine, were targeted. Users faced intermittent outages, and the company had to take its system status page offline due to unrelated technical issues. To prevent future incidents, Threema has implemented specialized DDoS protection measures. The company communicated with business customers about the unstable service conditions during the attacks.

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Timeline

2026-08-15
DDoS attacks began
Users reported service interruptions on Threema, particularly in Switzerland, India, and China.
Bleepingcomputer
2026-08-15
Initial response from Threema
Threema attributed the initial outages to a network issue with their colocation partner.
Bleepingcomputer
2026-08-16
Confirmation of DDoS attacks
Threema confirmed ongoing DDoS attacks targeting both their service and colocation partner Nine.
Securityaffairs.Co
2026-08-16
Mitigation efforts announced
Threema announced the implementation of specialized DDoS protection to mitigate future attacks.
Bleepingcomputer

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