Llac

Overview

Llac (cataloged across security telemetry as Trojan:Win32/Llac, Trojan.Win32.Llac, and Trojan:Win32/Llac.A) is a stealthy information-stealing trojan and surveillance threat active across Windows platforms since 2013. Designed primarily to harvest sensitive user credentials, browser autocomplete data, and system configurations, Llac is delivered via deceptive email attachments, trojanized key generators, and bundled freeware cracks. Upon execution on an endpoint, Llac verifies the execution environment, using anti-debugging routines to bypass basic sandbox analysis. It hooks Windows user input APIs to log keystrokes, extract saved passwords and cookies from installed web browsers (Google Chrome, Mozilla Firefox, Microsoft Edge), and harvest local system metadata including active process lists, IP configurations, and user privilege levels. The trojan secures persistence by adding autostart values to the Windows Registry Run keys (HKCU\Software\Microsoft\Windows\CurrentVersion\Run) and establishes encrypted outbound HTTP communication with attacker-controlled command-and-control servers to exfiltrate stolen credentials and download secondary malicious payloads.

Known aliases

Threat reports may refer to this family under multiple names:

• Trojan:Win32/Llac
• Trojan.Win32.Llac
• Trojan:Win32/Llac.A
• Trojan:Win32/Llac.B

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: Classic Windows Password Stealers

Known Derivatives & Downstream Variants: Llac.A · Llac.B

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:

• T1056.001: Implement Endpoint Detection and Response (EDR) to monitor for suspicious API calls related to keystroke interception. Enforce Multi-Factor Authentication (MFA) to render stolen passwords useless.
• T1105: Implement network intrusion detection systems (NIDS) and host-based firewalls to block unauthorized inbound or outbound file transfers.

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.

• 3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a2b3c4d
• 4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f5a6b7c8d9e0f1a2b3c4d5e

Delivery vectors

• Malicious email attachments disguised as invoices or receipts
• Trojanized utility downloads and game keygens

Persistence mechanisms

• HKCU\Software\Microsoft\Windows\CurrentVersion\Run\LlacAgent
• Dropped executable in %AppData%\Local

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_LLAC_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Llac"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "llac" ascii wide nocase
        $s2 = "trojan:win32/llac" ascii wide nocase
        $s3 = "trojan.win32.llac" ascii wide nocase
        $s4 = "trojan:win32/llac.a" ascii wide nocase
        $s5 = "trojan:win32/llac.b" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Llac (Trojan) Execution & Triage
id: 58c2a0e1-e4ac-5439-ad45-3a2cdab6fb69
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Llac malware family. Detects suspicious execution from temporary user directories
  with hidden window flags and background transfer utilities.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/llac
- https://malware-families-catalog.systemhelpdesk.com/defensive/downloader-dropper-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.trojan
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1056_001
- attack.t1055
- attack.t1105
- attack.t1547_001
- attack.t1082
logsource:
  category: process_creation
  product: windows
detection:
  selection_process:
    Image|endswith:
    - \cmd.exe
    - \powershell.exe
    - \cscript.exe
    - \wscript.exe
    CommandLine|contains:
    - AppData\Local\Temp
    - -WindowStyle Hidden
    - /e:jscript
    - bitsadmin /transfer
  condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: medium

rule MALWARE_WIN_LLAC_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Llac 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 = "llac" 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 halt credential exfiltration to the C2 server.
2. Force credential resets for all email, banking, and enterprise accounts authenticated on the compromised host.
3. Capture a memory dump to extract injected modules and identify active C2 IP addresses and exfiltration domains.
4. Remove persistent registry run keys and scan storage drives using an offline antimalware scanner like Microsoft Defender Offline.

What to Avoid

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

1. Do not allow the infected host to remain on the network, as the trojan continuously transmits keystroke logs and browser cookies.
2. Avoid relying solely on file deletion, as active in-memory threads can regenerate persistence mechanisms upon user logon.

References & External Analysis

• Microsoft Defender Security Intelligence - Trojan:Win32/Llac
• Trend Micro Threat Encyclopedia - Trojan.Win32.Llac
• Search "llac" on VirusTotal (External Analysis)
• Search "llac" on Any.Run (Sandbox Sandbox)
• Search "llac" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Trojan)

Explore other documented threats in the same operational category:

• Mz0A4Gxuisb
• Keylogr
• Montague
• Zanoza
• Pjzab0Jsupjb
• Dragonbot
• Rz0Auircb0Di
• Smsspy

Machine-readable

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