Was Triathlon.group hit by ransomware?

Triathlon.group was listed by the Underground ransomware operation (Germany), and stolen data was published on the group's leak site. Darkfield tracks this disclosure with the original leak post, screenshot and group context.

Who is the Underground ransomware group?

Underground is a ransomware operator tracked by Darkfield. See the full operator dossier for its known victims, sectors targeted, IOCs and leak-site infrastructure.

What data was leaked in the Triathlon.group breach?

Underground published data attributed to Triathlon.group. Darkfield captured the leak post and a screenshot of the listing.

Ransomware victim disclosure

← All victims

Sunlight Group (Triathlon Systems division)

listed as Triathlon.group · Claimed by Underground · listed 2 years ago

$176M

Ransom

demanded

26m

Age

since listed · data leaked

Status timeline

ListedMay 1, 2024
Data leakeddate unknown

At a glance

Group: Underground
Status: Data leaked
Country: Germany
Sector: Transportation/Logistics
Listed on leak site: May 1, 2024
Ransom demanded: $176M
Estimated revenue: $176M

About the victim

AI dossier — public-source company profile

Sunlight Group is a global energy storage and battery manufacturer with 30+ years of experience, operating 35+ facilities across 115+ countries. Triathlon Systems is one of its subsidiary companies within the ecosystem of industrial battery and energy solutions.

Industry: Energy Storage Systems & Industrial Batteries

Attack summary

Severity: medium — Data published status with significant claimed ransom ($176M) suggests exfiltration occurred, but no specific data categories or proof files are detailed in the truncated post. Industrial/manufacturing data exposure is moderate concern; no PII or regulated sector explicitly mentioned.

The Underground group claims to have attacked Sunlight Group/Triathlon Systems and lists a $176M revenue figure associated with the victim. The leak post does not explicitly state what data was exfiltrated or the attack method (encryption vs. exfiltration only).

medium

What the group claims

Revenue:$176M - Country :Australia, Germa...

Sources

Source

Indexed 2 years ago

This page surfaces a public ransomware disclosure indexed by Darkfield. Original posts come from the operator's own leak site; we cross-check against ransomware.live, RansomLook and RansomWatch where applicable. Share this URL freely.

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Disclosure context

About Underground

Underground is a relatively new ransomware group that emerged in May 2024, primarily motivated by financial gain through extortion operations targeting organizations across multiple sectors. The group's origin and affiliations remain largely undocumented in public threat intelligence reporting, with no confirmed details about their country of origin or whether they operate as an independent entity or through a Ransomware-as-a-Service model. Based on the limited public information available, Underground has demonstrated a preference for targeting technology, healthcare, business services, manufacturing, and agriculture sectors, with their attacks concentrated primarily in the United States, Canada, South Korea, Germany, and Taiwan. The group's specific attack methodologies, initial access vectors, and technical capabilities have not been extensively documented in publicly available threat intelligence reports from major security firms or government agencies. With only 26 known victims since their emergence in May 2024, Underground represents a smaller-scale operation compared to established ransomware groups, though their cross-sector targeting approach indicates opportunistic victim selection rather than specialized industry focus. Given the recent emergence of this group and limited public reporting, Underground appears to remain active but operates at a relatively low profile compared to more established ransomware families. The group has been linked to 26 public disclosures across our corpus. First observed on a leak site on May 1, 2024; most recent post August 15, 2025. The operation is currently inactive.

Timeline of this disclosure

May 1, 2024Triathlon.group listed by Undergroundon the group's public leak site

Ransom demanded: $176M

Other recent disclosures by Underground

Underground has been linked to 26 public victims on Darkfield. A sample of the most recent:

See the full Underground dossier →

Sector and geography

This disclosure adds to ransomware activity in the Transportation/Logistics sector, which has 1,081 disclosures indexed across all operators we track. Geographically, Triathlon.group is reported in Germany, a country with 926 ransomware disclosures in our corpus.

If your organisation is affected

A listing by Underground means Triathlon.group 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.
Report the incident to your national CERT, CERT-Bund (Germany), as required for your jurisdiction.
Monitor for the data appearing on Underground'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.