Atomsilo is a relatively obscure ransomware group that emerged in December 2021, operating with financial motivations and maintaining a low profile compared to major ransomware operations. The group's origin and potential affiliations remain largely undocumented by major threat intelligence sources, though their limited scope of operations suggests they function as an independent entity rather than a large-scale Ransomware-as-a-Service operation. Based on available victim data, Atomsilo appears to employ targeted attacks against specific sectors, though their exact initial access vectors and technical methodologies have not been extensively documented by major security research organizations. The group has demonstrated a preference for targeting healthcare and financial services sectors, with documented activity primarily affecting organizations in Brazil and Japan, suggesting either regional focus or specific linguistic/cultural targeting capabilities. Atomsilo remains a minor player in the ransomware landscape with only five publicly documented victims, and their current operational status is unclear due to limited public reporting and analysis from major threat intelligence sources. The group has been linked to 5 public disclosures across our corpus. First observed on a leak site on December 21, 2021; most recent post February 24, 2026. The operation is currently active.
If your organisation is affected
A listing by Atomsilo means LIGHT CONVERSION appeared on a ransomware extortion site and data attributed to it has been published. If this is your organisation, or a supplier you depend on, the priority is to confirm the intrusion and contain it before the window to act closes.
- Engage your incident-response team and preserve forensic evidence before remediating — do not wipe affected systems first.
- Force a password reset and revoke active sessions for exposed accounts; rotate any credentials, API keys or certificates that may have been in the stolen data.
- Assess regulatory notification duties (GDPR, NIS2, sector regulators) — many carry a 72-hour reporting clock from awareness.
- Monitor for the data appearing on Atomsilo's leak site and across paste and breach channels, and brief downstream partners who may be exposed through you.
How we know this. Darkfield monitors public ransomware leak sites continuously, archiving every new disclosure and the data later released against the victim. Each entry on this page is sourced from the operator's own publication and cross-checked against complementary OSINT feeds (RansomLook, ransomware.live, RansomWatch). We do not collect or host stolen data — only the metadata, timestamps and screenshots needed to make the public disclosure searchable and accountable. Records here are corrected when the original post is edited, retracted, or merged with another disclosure.
