Microsoft says Outlook outage earlier this month caused by cyberattacks

Earlier this month, Microsoft 365 suite, which includes Outlook, Word and Excel, was down for thousands of users, outage tracking website Downdetector showed. At that time, Microsoft 365 Status account tweeted about the outage that occurred on June 5, and a day later said that it got things under control. However, the company was investigating the cause of the outage and it has now added that outages were caused by a Distributed Denial-of-Service (DDoS) attack.
“Beginning in early June 2023, Microsoft identified surges in traffic against some services that temporarily impacted availability.Microsoft promptly opened an investigation and subsequently began tracking ongoing DDoS activity by the threat actor that Microsoft tracks as Storm-1359,” the company said in a blog post.
A DDoS attack is a type of cyberattack wherein hackers make a malicious attempt to disrupt the normal traffic of a server, service or network by overwhelming the target or its surrounding infrastructure with internet traffic.
“These attacks likely rely on access to multiple virtual private servers (VPS) in conjunction with rented cloud infrastructure, open proxies, and DDoS tools,” it added.
Group believed to be Russian
According to a report by news agency The Associated Press, a spokesperson from Microsoft confirmed that the group that calls itself Anonymous Sudan was behind the attacks. It claimed responsibility on its Telegram social media channel at the time. Some security researchers believe the group to be Russian.
It, however, did not offer details on how many customers were affected and whether the impact was global. “We have seen no evidence that customer data has been accessed or compromised,” the company said.
According to Microsoft, the DDoS activity targeted layer 7 rather than layer 3 or 4. “Microsoft hardened layer 7 protections including tuning Azure Web Application Firewall (WAF) to better protect customers from the impact of similar DDoS attacks,” it added.
Several users claimed during the attack that their Outlook desktop stopped working for them. The affected people, which included both Windows and macOS users, said that they were unable to send emails.