Lsslogger

Overview

Trojan:Win32/Lsslogger is a specialized, stealthy trojan designed exclusively for credential theft, specifically operating as a **Keylogger**. Unlike broad information stealers that simply scrape browser files, Lsslogger focuses on intercepting user input at the operating system level, capturing passwords, emails, and sensitive communications as they are typed, before they are encrypted by applications.

Understanding Lsslogger (Keyloggers)
To an end-user, Lsslogger is completely invisible; it does not display windows or impact performance. For a security analyst, a keylogger represents a severe breach of confidentiality. It implies that any credential entered on the compromised machine (including highly secure passwords not saved in browsers) is now in the hands of the attacker, often facilitating immediate lateral movement.

Execution and Interception Mechanics
Lsslogger is typically dropped by a primary infection vector, such as a malicious Office macro (`T1566.001`) or a downloader trojan. Once executed, it establishes persistence via the Registry Run keys or hidden scheduled tasks (`T1547.001`). Its core function relies on hooking Windows APIs (`T1056.001`). It uses functions like `SetWindowsHookEx` to intercept keyboard events before they reach the target application (like a web browser or VPN client). The captured keystrokes are recorded into a hidden, often encrypted, log file stored in the `%Temp%` or `System32` directory. Periodically, Lsslogger compresses this log file and exfiltrates it to the attacker, often using simple protocols like SMTP (emailing the logs to a disposable address) or FTP upload (`T1048.003`).

Indicators of Compromise & Impact
The impact is the total compromise of all accounts accessed from the infected machine. Host-based IoCs include EDR alerts for 'Suspicious API Hooking' targeting input functions, and the presence of rapidly growing, encrypted `.dat` or `.log` files in user profile directories. Network IoCs often include anomalous outbound SMTP (port 25, 465, 587) or FTP (port 21) traffic originating from a standard Windows process rather than a legitimate email client.

MITRE ATT&CK Techniques

Observed techniques used by this family, mapped to the 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.

Generated Detections (Boilerplate)

These YARA and Sigma rules are auto-generated based on the family name and aliases. They must be heavily tuned before deployment in a production environment.

YARA Rule

rule MALWARE_WIN_LSSLOGGER {
    meta:
        description = "Detects Lsslogger (trojan)"
        author = "SystemHelpdesk Boilerplate Generator"
        date = "2026-07-06"
    strings:
        $s1 = "lsslogger" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

Sigma Rule

title: Suspicious Lsslogger Activity
id: 669532e38a8124cbbf2547ccbec50a6a
status: experimental
description: Detects generic indicators of the lsslogger malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*lsslogger*"
    condition: selection
level: medium

Containment & Response Steps

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

1. Assume ALL credentials typed on the machine (corporate passwords, personal banking, SSH keys) are compromised and force immediate resets from a known-clean device.
2. Isolate the endpoint to stop the active exfiltration of the keylogger log files.
3. Analyze the memory of running processes to identify the specific module performing the API hooking and extract its configuration (which will reveal the attacker's email/FTP drop zone).
4. Review authentication logs across the network for the compromised user's credentials to detect if the attacker has already used the stolen passwords for lateral movement.

What to Avoid

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

1. Do not assume multi-factor authentication (MFA) provides complete protection; while it helps, a keylogger will capture the username and password, giving the attacker half of what they need.
2. Avoid relying solely on file deletion; advanced keyloggers often inject their hooking DLLs into legitimate processes like `explorer.exe`, requiring a reboot or process termination to fully unload.

References & External Analysis

• Search "lsslogger" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: trojan)

Explore other malware families in the same category:

• Netdevil
• Hmgfa45Id4O
• Xxybzx
• Stubrc
• Scrop

Machine-readable

Get this profile as JSON: https://jordanricky1604-ship-it.github.io/malware-families-catalog/api/lsslogger.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.