Worldwide list of DDoS attacks took place during the month of May 2021
| Date of attack | Country | Industry | Downtime | Company Affected | Size of Company | Attack Details | Press Link |
| May 19 | New Zealand | Healthcare | 2 Weeks | Waikato District Health Board | NA | Twice the usual time to treat patients, following a crippling DDoS attack that halted operations. | Click here |
| May 18 | Ireland | ISP | NA | Nova Broadband | Small | Network went down causing connectivity issues. However, no compromise of systems or data. | Click here |
| May 18 | France | Insurance | Few Hours | AXA | Enterprise | AXA’s websites in Thailand, Malaysia, Hong Kong, and the Philippines went down. | Click here |
| May 14 | Ireland | Government | 1 Day | Health Service Executive (HSE) | NA | DDoS attacks forerunner for a larger ransomware attack. | Click here |
| May 5 | Australia | Telco | Several Days | Schepisi Communications | Enterprise | A Telstra platinum partner, knocked offline by a ransomware group threatening data leakage unless demands met. | Click here |
| May 4 | Belgium | Telco | 1 Day | Belnet | Enterprise | Traffic from 29 countries flooded networks, affecting 200 organizations, raising connectivity issues for customers. | Click here |
