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.
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, Simmtech Co., Ltd. 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.
