Krilog

Overview

Spyware:Win32/Krilog (or Keylogger:Win32/Krilog) is a malicious tool designed specifically to capture a user's keystrokes (`T1056.001`), mouse clicks, and sometimes screen contents (`T1113`) without their knowledge or consent. It is a primary tool used by attackers for credential harvesting, corporate espionage, and identity theft.

Understanding Krilog (Keylogger)
To an end-user, a Krilog infection is entirely invisible; the software is designed specifically to hide its presence while silently recording activity. For a SOC analyst, a keylogger detection implies a total compromise of confidentiality for that host. Every password typed, every email drafted, and every secure portal accessed while the keylogger was active must be considered compromised.

Execution and Data Capture Mechanics
Krilog is typically dropped by a primary infection vector (like a trojan delivered via malspam). Once active, it uses low-level Windows APIs (such as `SetWindowsHookEx`) to intercept hardware events before they reach the intended application (`T1056.001`). It records these events into a hidden, encrypted log file (often stored in `%Temp%` or `%AppData%`). On a scheduled basis, Krilog bundles this log file and exfiltrates it to the attacker's C2 server (`T1041`), often via SMTP (email), FTP, or HTTP POST.

Indicators of Compromise & Impact
The impact is severe credential compromise and data theft. Host-based IoCs include EDR alerts for suspicious API hooking (e.g., a non-standard process injecting hooks into `explorer.exe` or browser processes). The presence of hidden, rapidly growing text or encrypted files in user profile directories is a strong indicator. Network IoCs involve regular, small bursts of outbound traffic (often SMTP or FTP) corresponding to the exfiltration of the keylog files.

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.

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_KRILOG_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Krilog"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "krilog" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Krilog (Trojan) Execution & Triage
id: 360bc215-c5ac-5942-add3-3dfa34d5ae8f
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Krilog 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/krilog
- 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.t1041
- attack.t1055
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_KRILOG_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Krilog 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 = "krilog" 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 to prevent any further exfiltration of the captured keystrokes.
2. Assume all passwords typed on this machine since the estimated time of infection are compromised; force immediate password resets across all corporate accounts.
3. Analyze the exfiltrated log files (if they can be recovered locally) to determine exactly what sensitive data was stolen.
4. Use EDR or AV to identify and remove the Krilog executable and its associated registry persistence keys.

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 user to type their new passwords on the infected machine until it has been completely wiped and re-imaged.
2. Avoid closing the incident after removing the malware; the stolen credentials represent an ongoing threat.

References & External Analysis

• Search "krilog" on VirusTotal (External Analysis)
• Search "krilog" on Any.Run (Sandbox Sandbox)
• Search "krilog" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Trojan)

Explore other documented threats in the same operational category:

• Seznam
• Vindor
• Netpass
• Z_Dem0N
• Stormattack
• Installflash
• Y3K_Rat
• Ursnifdropper

Machine-readable

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