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

August 15, 2025SFA Engineering listed by Undergroundon the group's public leak site

Data size: 2.3 TB
Ransom demanded: $1.7B

Sector and geography

This disclosure adds to ransomware activity in the Technology sector, which has 2,524 disclosures indexed across all operators we track. Geographically, SFA Engineering is reported in South Korea, a country with 32 ransomware disclosures in our corpus.

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.

Ransomware victim disclosure

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SFA Engineering

Claimed by Underground · listed 9 months ago

2.3 TB

Data size

$1.7B

Ransom

demanded

Age

since listed · data leaked

Status timeline

Listed
Aug 15, 2025
Data leaked

At a glance

Group: Underground
Status: Data leaked
Country: South Korea
Sector: Technology
Listed on leak site: Aug 15, 2025
Data size: 2.3 TB
Ransom demanded: $1.7B
Estimated revenue: $1.7B

About the victim

AI dossier — public-source company profile

SFA Engineering is a South Korean engineering company. Limited publicly available information is available from the clearnet domain sfa.co.kr.

Industry: Engineering & Design

Attack summary

Severity: high — Confirmed data exfiltration of 2.3 TB with public disclosure; extremely high ransom demand ($1.7B) suggests significant data sensitivity or operational criticality, though specific data types are not detailed in the post.

The Underground group claims to have exfiltrated 2.3 TB of data from SFA Engineering. The group is demanding $1.7B ransom and has published the data on their leak site.

high

Data the group says was taken

AI dossier — extracted from the leak post

company records
business documents
technical files

What the group claims

Revenue: $1.7 Billion Type: Industry Size: 2,3 TBytes

The leak post

captured from the group's site

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Sources

Source

Indexed 9 months 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.