Guildma

Overview

Guildma (also tracked by cybersecurity researchers as Astaroth, Trojan:Win32/Guildma, and Trojan-Banker.Win32.Guildma) is a highly sophisticated, multi-stage modular banking trojan active since at least 2015. Coined by Kaspersky's Global Research and Analysis Team (GReAT) as one of the four infamous 'Tetrade' Latin American banking malware families (alongside Javali, Melcoz, and Grandoreiro), Guildma originated in Brazil and subsequently expanded operations globally across Latin America, North America, and Europe. Guildma is delivered through high-volume, localized spearphishing campaigns masquerading as tax notices, utility bills, and legal subpoenas carrying weaponized ZIP, LNK, or VBScript attachments. The infection chain relies heavily on Living-off-the-Land Binaries (LOLBins)—abusing BITSAdmin, certutil, and Windows Script Host—and hides payload modules using NTFS Alternate Data Streams and DLL search-order hijacking. To orchestrate stealthy command-and-control communication, Guildma embeds encrypted C2 configurations directly into descriptions on legitimate platforms such as YouTube videos and Facebook profiles. Once active, the trojan monitors browser processes, deploying automated web-injects and hidden VNC (hVNC) sessions to hijack active banking and cryptocurrency sessions, intercepting multi-factor authentication (MFA) tokens in real time.

Known aliases

Threat reports may refer to this family under multiple names:

• Trojan:Win32/Guildma
• Astaroth
• Guildma
• Trojan-Banker.Win32.Guildma
• Win32/Guildma
• Tetrade.Guildma

Family Pedigree & Lineage

Malware authors regularly fork and iterate upon existing codebases. Observed upstream lineage and downstream variants for this family include:

Derived From / Upstream Ancestry: Brazilian Banking Trojans · Tetrade Group Malware

Known Derivatives & Downstream Variants: Guildma V1 · Astaroth Multi-Stage · Ghimob Mobile Rat

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to our technical analysis hubs and the official MITRE ATT&CK framework:

Tactical Mitigations

Based on the techniques used by this family, consider the following defensive strategies:

• T1056.004: Monitor for unauthorized keylogging, screen capturing, or web browser API hooking. Deploy EDR to detect API hooking.
• T1105: Implement network intrusion detection systems (NIDS) and host-based firewalls to block unauthorized inbound or outbound file transfers.
• T1185: Enforce strong MFA and use browser isolation or hardened browsers for sensitive financial or administrative portals to defeat session hijacking.
• T1566.001: Scan email attachments for malicious macros, scripts, or suspicious archive files.

MITRE D3FEND™ Defensive Countermeasures

Defensive techniques mapped to counter the offensive tradecraft observed in this family (via the MITRE D3FEND matrix):

Indicators of Compromise

Public indicators drawn from CISA advisories and vendor reporting. These are historical and intended for retrospective threat hunting; current campaigns may use different infrastructure. SystemHelpDesk adheres to responsible disclosure and does not host live samples.

File hashes (SHA-256, sample)

Cryptographic hashes serve as reference indicators for triage and detection rules. In accordance with responsible threat intelligence disclosure, this catalog indexes reference metadata and does not host or distribute live malware binaries.

• 3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b
• 4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c

Delivery vectors

• Spearphishing emails with malicious LNK or VBS attachments in ZIP archives
• BITSAdmin and certutil payload downloading routines

Persistence mechanisms

• HKCU\Software\Microsoft\Windows\CurrentVersion\Run\GuildmaLoader
• NTFS Alternate Data Streams (ADS) staging scripts

Tiered Detection Rules (Cisco CAIRN Model)

Modern threat detection requires multi-layered rule engineering. We classify detections into three operational tiers based on signal fidelity:

rule MALWARE_WIN_GUILDMA_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Guildma"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "guildma" ascii wide nocase
        $s2 = "trojan:win32/guildma" ascii wide nocase
        $s3 = "astaroth" ascii wide nocase
        $s4 = "guildma" ascii wide nocase
        $s5 = "trojan-banker.win32.guildma" ascii wide nocase
        $s6 = "win32/guildma" ascii wide nocase
        $s7 = "tetrade.guildma" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Guildma (Banking Trojan) Execution & Triage
id: 7b0edae0-ef84-510c-8a4b-c4a64b9720fb
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Guildma malware family. Detects recon staging, certutil file payload staging,
  and web-inject process proxying characteristic of banking trojan initial loaders.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/guildma
- https://malware-families-catalog.systemhelpdesk.com/defensive/banking-trojan-protection
- https://malware-families-catalog.systemhelpdesk.com/
author: Ricky Jordan, Lead Threat Intelligence Analyst, SystemHelpDesk MSP
date: '2026-10-14'
modified: '2026-10-14'
tags:
- attack.banking-trojan
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1566_001
- attack.t1055
- attack.t1197
- attack.t1056_004
- attack.t1185
logsource:
  category: process_creation
  product: windows
detection:
  selection_process:
    Image|endswith:
    - \svchost.exe
    - \explorer.exe
    - \msiexec.exe
    - \certutil.exe
    CommandLine|contains:
    - -urlcache
    - -split -f
    - ipconfig /all
    - route print
    - netstat -ano
  condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: high

rule MALWARE_WIN_GUILDMA_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Guildma tradecraft"
        tier = "T3 - Attribution Fingerprint"
        confidence = "High (Confirmed Family Signature)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        // Core family identifier & heuristic payload signatures
        $attrib_str = "guildma" ascii wide nocase
        $pe_magic = "MZ" ascii
        $net_marker = "http" ascii nocase
    condition:
        uint16(0) == 0x5a4d and ($attrib_str and $net_marker) and filesize < 15MB
}

Containment & Response Steps

Ordered checklist for responders. Adapt to your environment and engage professional support for active incidents.

1. Immediately disconnect the endpoint from network and internet interfaces to sever active hVNC remote-control sessions.
2. Contact corporate and personal financial institutions to freeze affected accounts, review recent transfers, and revoke session tokens.
3. Capture a full volatile memory dump prior to rebooting to preserve decrypted web-inject rules and active C2 endpoints.
4. Perform an exhaustive operating system reimaging, as Guildma embeds deep system hooks and NTFS alternate stream files.

What to Avoid

Common mistakes during response to this family that can destroy evidence, spread the infection, or worsen recovery.

1. Do not permit users to log in to online banking or corporate portals from an endpoint flagged with Guildma activity.
2. Avoid rebooting endpoints before dumping RAM, as volatile web-inject configuration files reside purely in memory.

References & External Analysis

• Kaspersky Securelist - The Tetrade: Brazilian Banking Trojans Go Global
• Microsoft Defender Threat Intelligence - Astaroth Fileless Threat Analysis
• Search "guildma" on VirusTotal (External Analysis)
• Search "guildma" on Any.Run (Sandbox Sandbox)
• Search "guildma" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Banking Trojan)

Explore other documented threats in the same operational category:

• Spyeye
• Sinowal
• Bestafera
• Dreambot
• Qbot
• Mekotio
• Clipbanker
• Blackmoon

Machine-readable

Get this profile as JSON: https://malware-families-catalog.systemhelpdesk.com/api/guildma.json

Ecosystem & Interactive Environments

This profile is part of the Malware Families Catalog, a public dataset of 2,899 malware families. The catalog is also published across our ecosystem: Hugging Face, Kaggle, Zenodo, Replit, StackBlitz, CodeSandbox, and CodePen.