Introduction
Beginning in 2024 Mandiant investigated a string of compromises affecting Brazilian financial services, retail, and eCommerce organizations. Google Threat Intelligence Group (GTIG) tracks this activity as BREEZE COMET (formerly UNC5669), a financially motivated threat actor specializing in manipulating payment systems and banking software in Brazil to conduct fraudulent transfers. This activity overlaps with operations publicly reported as Plump Spider and SHADOW-AETHER-064. In this blog, we detail BREEZE COMET’s tactics and toolkit, and provide mitigation recommendations and detections to support organizations in defending against this active and developing threat.
BREEZE COMET tactics have evolved over time to leverage a customized malware suite and compromised, trusted websites to facilitate initial access, command and control (C2), and to interact with financial software and payment APIs. BREEZE COMET’s operational infrastructure may also indicate intent to expand their infrastructure footprint to other countries in Latin America and Africa. Additionally, we have evidence that BREEZE COMET is using generative artificial intelligence (AI) to support malware development, which may further increase the scale, speed, and sophistication of their operations in the future.
BREEZE COMET Targets Brazilian Financial Technology
BREEZE COMET operations target organizations with permission to conduct transactions through banking software, APIs, and payment systems such as Pix, STR, and Boleto. This typically includes banks, payment processors, retailers, exchanges, as well as fintech and banking software providers.
To achieve their objective of conducting fraudulent transfers, BREEZE COMET must maintain:
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Access to the National Financial System Network (Rede Nacional do Setor Financeiro, RSFN) through an entity with this access.
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Access to mTLS credentials that allow sending authenticated payloads with transactional orders to Pix, STR (Brazilian Reserves Transfer System), or any transactional listener to be executed with minimal restrictions in the name of an organization with available funds.
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Persistent access to multiple accounts in targeted organizations’ Active Directory and/or cloud environments.
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Understanding of an organization’s transfer processing procedures, network controls, fintech integrations and anti-fraud systems.
In order to support these requirements, BREEZE COMET evolved to operate in multiple compromised environments at the same time, crafting custom C2 malware to automate activities such as reconnaissance, lateral movement, persistence, and exfiltration.
Initial Compromise and Establish Foothold
BREEZE COMET has used various methods for initial access. In early compromises, Mandiant observed this threat actor use password spraying as well as voice calls impersonating IT support teams to convince users to install Remote Monitoring and Management (RMM) tools such as AnyDesk. Axur corroborates use of voice phishing, and suggests that the group has also attempted to recruit insiders at targeted organizations.
In mid-2025, GTIG observed BREEZE COMET using compromised Brazilian small government websites to stage RMM tools, infostealers disguised as legitimate tax or receipt documents (e.g., ComprovantePDF.exe), or backdoors such as XWORM set to persist via automated startup shortcut modifications. XWORM is a backdoor that is widely available for purchase on cyber crime forums, with leaked or “cracked” versions also available. BREEZE COMET then used these compromised government websites to facilitate social engineering operations for initial access, and as C2 endpoints. The use of compromised, trusted infrastructure allowed the threat actors to avoid detection by network domain reputation filters. GTIG also observed BREEZE COMET replicating this behavior with municipal domains in Nigeria, Paraguay, Ghana, and Venezuela, suggesting a potentially growing targeting focus. Analysis of compromised municipal domains indicated that BREEZE COMET reused the same staging infrastructure to host and deliver XWORM payloads across operations targeting multiple organizations.
In 2025, we first observed BREEZE COMET connect rogue hardware devices directly into retail store networks to establish footholds into targeted environments. From this initial network access, BREEZE COMET moved laterally to internal systems then downloaded the Netcat utility alongside custom scripts to pull down subsequent post-exploitation frameworks from external open directories. Trend Micro has reported that the group also exploited vulnerabilities in JBoss AS servers to gain initial access.
Escalate Privileges & Internal Reconnaissance
BREEZE COMET used publicly available reconnaissance utilities such as Impacket, ADRecon and ADVipscan, as well as with custom malware, often profiting from environments with low observability. These utilities were often observed being downloaded from GitHub repositories and executed in memory via PowerShell for defense evasion.
The threat actor deployed the custom LDAP brute-forcing utility REALBREEZE. Beyond traditional Active Directory compromise, BREEZE COMET specifically targets development and cloud environments to escalate privileges. The group actively mines continuous integration and continuous delivery (CI/CD) environments to steal hard-coded pipeline credentials, application programming interface (API) keys, and highly privileged cloud access tokens.
BREEZE COMET used custom scripts to search internal host files and environmental variables to identify mTLS credentials and administrative certificates necessary to authenticate against core banking systems. Observed search terms included: boleto, cnab, remessa, webhook.*pix and instant.*payment.
Move Laterally
BREEZE COMET abuses standard protocols to navigate the network, using hijacked service accounts to initiate unauthorized Remote Desktop Protocol (RDP) sessions and execute commands via SMB network file shares. BREEZE COMET was observed executing network scanning tools across internal subnets specifically to enumerate available SMB pathways.
To maneuver through segmented financial networks and bypass strict internal firewalls, BREEZE COMET deploys specialized routing malware: COBALTSPIN. Written in Rust, COBALTSPIN operates as a lightweight, evasive network tunneler, used to communicate with and maintain persistent network access to financial API infrastructure. By establishing a reverse SOCKS5 proxy over a WebSocket connection, COBALTSPIN routes network traffic securely back and forth between the C2 and internal targets, enabling lateral movement directly through boundary firewalls without requiring built-in persistence mechanisms that might trigger detection.
