Zusy

Overview

Tinba (formally designated in AV classification as Zusy or IlliBanker, and colloquially celebrated as the 'Tiny Banker') is a notoriously compact banking trojan first analyzed in May 2012 by CSIS Security Group. Weighing in at approximately 20 kilobytes in compiled binary size, Tinba achieved legendary status among reverse engineers for accomplishing full-featured man-in-the-browser (MitB) financial theft within an extraordinarily minimalist, hand-crafted x86 assembly footprint. Tinba hooks Windows networking APIs (specifically in ws2_32.dll, wininet.dll, and nspr4.dll) to intercept HTTPS traffic before encryption. When victims navigate to targeted banking portals, Tinba injects fraudulent HTML/JavaScript form fields into the webpage, prompting users for sensitive details such as debit card PINs, mother's maiden names, and one-time SMS authentication codes. In July 2014, Tinba's complete source code leaked onto Russian cybercrime forums, leading to widespread proliferation and the development of Tinba v2 with domain generation algorithm (DGA) capabilities.

Known aliases

Threat reports may refer to this family under multiple names:

• Tinba
• Tiny Banker
• Zusy
• IlliBanker
• TinyBanker

Threat Actor Attribution

Attribution is probabilistic, not a science. Each link below states its confidence level and the evidence behind it.

• Underground Assembly Developer / Leaked Source Syndicates High confidence
  Basis: Originally created in 2012 as a hyper-compact 20 KB assembly-coded banking trojan. Following the public leak of its full source code in July 2014, multiple independent cybercrime operations deployed modified versions featuring domain generation algorithms (DGA) and localized webinjection kits. [source]

Family Pedigree & Lineage

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

Known Derivatives & Downstream Variants: Tinba V1 · Tinba V2 · Tinba-Dga

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:

• T1071.001: Implement web filtering and SSL/TLS inspection to detect malicious command and control (C2) traffic hiding in HTTP/HTTPS.
• T1185: Enforce strong MFA and use browser isolation or hardened browsers for sensitive financial or administrative portals to defeat session hijacking.
• T1566.002: Inspect email links for known malicious domains and use link-rewriting services for time-of-click analysis.

MITRE D3FEND™ Defensive Countermeasures

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

Exploited Vulnerabilities (CVEs)

This malware family is documented weaponizing the following common vulnerabilities and exposures:

• CVE-2013-3893 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).
• CVE-2014-0322 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).

Command & Control (C2) and Network Profile

How this family talks to its operators. C2 traffic can often identify a family even when its code and configuration are hard to analyse. Ports and patterns are historical and change between campaigns, so use them as hunting leads rather than block-only rules.

Network detection ideas

• Detect high volumes of NXDOMAIN responses matching Tinba DGA algorithm domain characteristics
• Inspect web browser processes (chrome.exe, firefox.exe, iexplore.exe) for inline hook modifications to WS2_32.dll and Wininet.dll
• Block network traffic to known Tinba C2 domains cataloged by abuse.ch Feodo Tracker

Sources: CISA Advisory AA20-302A, abuse.ch Feodo Tracker Tinba

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.

• 0e9cb293b610c1f5d6ee47ab95323eb71790ae4fe6b77ae4b0d0092cce53df4a
• 7a884fa6e3d5b087f94bb2e15bc963f45812e106987f2da542ec9a5180f63aa9

Delivery vectors

• Drive-by downloads from compromised websites hosting Nuclear and Rig Exploit Kits
• Phishing emails containing weaponized ZIP or DOC attachments

Persistence mechanisms

• Registry Run key in HKCU\Software\Microsoft\Windows\CurrentVersion\Run pointing to %APPDATA%\bin
• Process injection into explorer.exe and active web browser processes

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_ZUSY_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Zusy"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "zusy" ascii wide nocase
        $s2 = "tinba" ascii wide nocase
        $s3 = "tiny banker" ascii wide nocase
        $s4 = "zusy" ascii wide nocase
        $s5 = "illibanker" ascii wide nocase
        $s6 = "tinybanker" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Zusy (Banking Trojan) Execution & Triage
id: 7d4c4b45-e844-524b-aa6d-01ac89a06a21
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Zusy 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/zusy
- 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.t1185
- attack.t1071_001
- attack.t1055
- attack.t1547_001
- attack.t1555_003
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_ZUSY_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Zusy 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 = "zusy" 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. Isolate the endpoint immediately from the corporate network to prevent Zusy from executing real-time Automated Transfer System (ATS) fraudulent transactions or web injections.
2. Revoke all active online banking sessions, treasury management credentials, and accounting administrator sessions accessed from the machine.
3. Analyze browser process memory (hooks on wininet.dll, ws2_32.dll, nspr4.dll) to detect and eradicate injected Zusy fraud modules.
4. Notify internal financial compliance and partner banking institutions to place temporary fraud holds or elevated monitoring on relevant accounts.

What to Avoid

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

1. Do not permit financial transactions or banking portal access from any machine in the same broadcast domain until Zusy network activity is cleared.
2. Avoid relying solely on antivirus scans, as banking trojans frequently hook browser API calls directly in user-mode memory.

References & External Analysis

• Malpedia (Fraunhofer FKIE): Tinba (win.tinba)
• CISA Advisory: CISA Alert AA20-302A (Top Routinely Exploited Vulnerabilities)
• Search "zusy" on VirusTotal (External Analysis)
• Search "zusy" on Any.Run (Sandbox Sandbox)
• Search "zusy" on MalwareBazaar (Malware Samples)

North American Authority Advisory (CISA / NIST)

The Cybersecurity and Infrastructure Security Agency (CISA) has published an official US federal advisory on this family, which can be mapped to NIST Cybersecurity Framework (CSF) incident response controls: CISA Alert AA20-302A (Top Routinely Exploited Vulnerabilities) ↗

Frequently Asked Questions

Related Threats (Category: Banking Trojan)

Explore other documented threats in the same operational category:

• Chthonic
• Shiz
• Trickster
• Alien
• Gozi
• Clipbanker
• Dridex
• Shiotob

Machine-readable

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