Ainslot

Overview

Trojan:Win32/Ainslot (also cataloged in threat telemetry as Worm:Win32/Ainslot.A, TROJ_GEN.UAE171Y, or Win32/Ainslot) is a persistent Windows trojan dropper and network worm designed to propagate across local network environments and deploy secondary crimeware. Ainslot spreads by scanning local subnet IP ranges for open network shares and utilizing weak administrative credentials, while also deploying via infected removable USB storage media. Once installed on a host system, Ainslot establishes persistence via the Windows Registry Run keys, communicates with remote C2 infrastructure using HTTP POST requests, and acts as a loader to drop auxiliary infostealers, password stealers, or generic trojan agents onto compromised endpoints.

Known aliases

Threat reports may refer to this family under multiple names:

• Ainslot
• Trojan:Win32/Ainslot
• Worm:Win32/Ainslot.A
• TROJ_GEN.UAE171Y
• Win32/Ainslot
• Trojan.Ainslot
• Downloader.Ainslot

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: Win32 Network Worm / Dropper Lineage

Known Derivatives & Downstream Variants: Worm:Win32/Ainslot.A · Trojan:Win32/Ainslot.B · Troj_Gen.Uae171Y

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:

• T1059.003: Restrict execution of Windows Command Shell (cmd.exe) and block unauthorized batch scripts.
• T1071.001: Implement web filtering and SSL/TLS inspection to detect malicious command and control (C2) traffic hiding in HTTP/HTTPS.

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.

• e7f8a9b0c1d2e3f4a5b6c7d8e9f0123456789abcdef0123456789abcdef0123
• fedcba9876543210fedcba9876543210fedcba9876543210fedcba9876543210

Delivery vectors

• Infected USB removable storage drives
• Network propagation across open SMB shares
• Phishing email attachments

Persistence mechanisms

• HKCU\Software\Microsoft\Windows\CurrentVersion\Run\AinslotService
• Autorun.inf on connected removable drives

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_AINSLOT_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Ainslot"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "ainslot" ascii wide nocase
        $s2 = "ainslot" ascii wide nocase
        $s3 = "trojan:win32/ainslot" ascii wide nocase
        $s4 = "worm:win32/ainslot.a" ascii wide nocase
        $s5 = "troj_gen.uae171y" ascii wide nocase
        $s6 = "win32/ainslot" ascii wide nocase
        $s7 = "trojan.ainslot" ascii wide nocase
        $s8 = "downloader.ainslot" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Ainslot (Trojan) Execution & Triage
id: 340bd0bc-cdb2-58c4-82f0-56c151532715
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Ainslot 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/ainslot
- 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.t1091
- attack.t1021_002
- attack.t1059_003
- attack.t1547_001
- attack.t1071_001
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_AINSLOT_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Ainslot 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 = "ainslot" 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. Sever network connectivity for the flagged endpoint to terminate persistent command-and-control (C2) communication channels and stop Ainslot from retrieving secondary stage payloads.
2. Capture process memory triage to detect and terminate malicious threads injected by Ainslot into legitimate system processes such as explorer.exe or svchost.exe.
3. Audit Windows Registry Run keys (HKCU\Software\Microsoft\Windows\CurrentVersion\Run) and Task Scheduler entries to locate and purge Ainslot persistence hooks.
4. Deploy updated enterprise EDR detection signatures and conduct an out-of-band endpoint scan to isolate dropped binaries and staged payloads.
5. Rotate all credentials, domain user passwords, and session cookies active on the system during the Ainslot execution timeframe.

What to Avoid

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

1. Do not assume the incident is resolved simply because an antivirus tool removed the initial Ainslot dropper; always verify that secondary payloads and persistence hooks have been eradicated.
2. Avoid logging in with Domain Admin or privileged credentials on a machine suspected of running Ainslot until memory triage is complete.
3. Do not delay host isolation; automated lateral movement and credential dumping can occur within minutes of initial execution.

References & External Analysis

• Microsoft Defender Threat Encyclopedia - Worm:Win32/Ainslot.A
• Trend Micro Threat Encyclopedia - TROJ_GEN.UAE171Y
• Kaspersky Threat Intelligence - Trojan.Win32.Ainslot
• Search "ainslot" on VirusTotal (External Analysis)
• Search "ainslot" on Any.Run (Sandbox Sandbox)
• Search "ainslot" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Trojan)

Explore other documented threats in the same operational category:

• Qqshou
• Bubbledock
• Pjzab0Jsupjb
• Trash
• Ayolog
• Qqrob
• Metel
• Brosafe

Machine-readable

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