Informer

Overview

Spyware:Win32/Informer is a persistent, stealthy spyware and keylogger designed to breach endpoint defenses and securely collect, log, and exfiltrate highly sensitive user activity, including keystrokes, screenshots, and clipboard data, to a remote attacker.

Understanding Informer Spyware
To an end-user, an Informer infection is entirely invisible. The software operates deep in the background, specifically designed to hide from the Task Manager and system tray. For a security analyst, discovering Informer on a corporate endpoint indicates a critical breach of privacy and a highly likely compromise of all credentials and sensitive communications entered on that machine.

Execution and Surveillance Mechanics
Informer is typically installed via spearphishing (`T1566.001`) bundled with an exploit or dropped by a primary trojan. Once executed (`T1204.002`), it establishes deep persistence, often by creating a hidden Windows Service (`T1543.003`) or manipulating the Registry Run keys (`T1547.001`). Its primary function is collection: it utilizes Windows API hooks (like `SetWindowsHookEx`) to log every keystroke (`T1056.001`), takes periodic hidden screenshots of the desktop (`T1113`), and captures clipboard data (`T1115`). The harvested data is then encrypted and silently emailed to the attacker or uploaded to a remote FTP server (`T1041`).

Indicators of Compromise & Impact
The primary impact is the catastrophic loss of confidentiality and credential compromise. EDR logs are critical for detecting this threat, specifically looking for processes injecting into `explorer.exe` or hooking the keyboard APIs. Network analysts should look for unauthorized, recurring outbound SMTP (email) or FTP traffic originating from the endpoint. Host-based IoCs include the presence of hidden, encrypted log files (often with extensions like `.dat` or `.log`) buried deeply in the `%AppData%` or `%ProgramData%` directories.

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.
• T1113: Monitor for frequent or unauthorized screen captures or clipboard reads. Restrict background applications from accessing desktop APIs.

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

Sigma Rule

title: Suspicious Informer Activity
id: 0881d037ec7c7fdb91964a8af52bd4e2
status: experimental
description: Detects generic indicators of the informer malware family.
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\cmd.exe'
            - '\powershell.exe'
        CommandLine|contains:
            - "*informer*"
    condition: selection
level: medium

Containment & Response Steps

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

1. Instantly isolate the endpoint to halt the exfiltration of the captured keystrokes and screenshots.
2. Enforce a mandatory, immediate password reset for *every* account the user has accessed from that machine, prioritizing domain credentials and VPN access.
3. Do not simply delete the executable; spyware often uses rootkit-like techniques to hide. Use an enterprise EDR solution to forcefully terminate the hooking service and clean the registry.
4. Perform a forensic review to determine how the software was installed (checking for phishing vectors).

What to Avoid

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

1. Do not assume only the local user's data was compromised; if an administrator logged into the infected machine, their credentials were also logged.
2. Avoid leaving the endpoint on the network while investigating, as the spyware will continue to transmit data in real-time.

References & External Analysis

• Search "informer" on VirusTotal (External Analysis)

Frequently Asked Questions

Related Families (Category: trojan)

Explore other malware families in the same category:

• Onesystemcare
• Korplug
• Mailspy
• Nemesis
• Umbra

Machine-readable

Get this profile as JSON: https://jordan123234-malware-families-explorer.static.hf.space/api/informer.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.