Ransomware attacks in May 2021: 169 confirmed incidents

// CONFIRMED RANSOMWARE ATTACKS · MONTH

Ransomnews has confirmed 169 ransomware attacks in May 2021, each one verified against a public source such as a breach notification, regulatory filing, court record or press report. That is 1.8% of the 9,520 confirmed incidents in the dataset. That compares with 184 in April 2021 and 95 in May 2020. The United States accounts for 81 of them (48%), with victims recorded in 33 countries in total. The most affected sector is healthcare, with 22 confirmed victims (13%). Where the operator is attributed, Avaddon leads with 22 confirmed victims. A ransom payment is on the public record in 5 cases and a refusal in 23; the outcome is unrecorded in the remaining 141.

Confirmed ransomware attacks by month, trailing 13 months to May 2021

Every month is a partial count until disclosures stop arriving, which typically takes three to four months. Compare May 2021 with months of the same age rather than with fully matured ones.

Which ransomware groups had the most confirmed victims in May 2021

The operator is attributed in 120 of the 169 confirmed incidents. Counts are confirmed victims, not leak-site claims, so they run well below the totals the groups publish about themselves. Group names link to the live Ransomtracker profile where one exists.

Where the confirmed attacks in May 2021 fall

Country shares carry a reporting bias. United States breach-notification law and SEC disclosure rules push far more incidents onto the public record than most jurisdictions, which makes American attacks easier to confirm and inflates the US share of any confirmed dataset.

Ransom payment outcomes in May 2021

Among the 28 confirmed incidents in May 2021 where the outcome is on the public record, 5 paid and 23 refused, a disclosed payment rate of 17.9%. The remaining 141 carry no public statement either way. Victims that pay have every incentive to stay quiet and public bodies are the most likely to announce a refusal, so treat this as the disclosed rate, not the true one. The ransomware payment rate analysis explains how the disclosed rate has moved since 2018 and how it compares with incident-response firm samples.

Largest confirmed ransomware attacks in May 2021 by records exposed

Record counts are recorded only where a named source disclosed them, which is the minority of cases, so this table ranks disclosed impact rather than true impact.

All confirmed ransomware attacks in May 2021

All 169 of 169 confirmed incidents. Every row links to the public source it was verified against.

Frequently asked questions

How to read this page. Every incident counted here was verified by Ransomnews against at least one public source. Leak-site listings alone do not qualify, because operators inflate, duplicate and occasionally fabricate claims, so these totals are a defensible floor rather than a full census. Records exposed and ransom outcomes appear only where a named source disclosed them. The page is regenerated from the live database, which refreshes weekly. Cite as: Ransomnews Confirmed Ransomware Attacks Dataset, ransomnews.com, with a link to this page. Bulk access and methodology questions: [email protected]. See also the monthly ransomware statistics and the Ransomtracker.