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

MITRE D3FEND™ Defensive Countermeasures

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

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_INFORMER_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Informer"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "informer" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Informer (Trojan) Execution & Triage
id: 32afab0a-1119-512c-afdf-979c605871e9
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Informer 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/informer
- 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.t1115
- attack.t1048_003
- attack.t1113
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_INFORMER_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Informer 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 = "informer" 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. 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)
• Search "informer" on Any.Run (Sandbox Sandbox)
• Search "informer" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Trojan)

Explore other documented threats in the same operational category:

• Karagany
• Mmnfbgfpueki
• Backswap
• Autocleanpro
• Snarasite
• Driverdevelop
• Fakesmoke
• Cool_Remote_Control

Machine-readable

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