Apost

Overview

APost (consistently cataloged across security research as Trojan:Win32/Apost, Trojan.Win32.APost, and Backdoor:Win32/Apost by Kaspersky, Trend Micro, and Microsoft Defender) is a targeted Windows trojan and spyware family active since 2012. Engineered primarily for covert reconnaissance, keystroke monitoring, and credential exfiltration, APost infiltrates endpoints through weaponized spearphishing email attachments, cracked application downloads, and drive-by web redirect chains. Once established on a target system, APost installs low-level Windows keyboard and mouse hooks, capturing keystrokes and active application titles to harvest enterprise credentials, banking logins, and corporate correspondence. Furthermore, the trojan takes periodic desktop screenshots, collects local system environment metadata (including active process trees, network interfaces, and user privileges), and establishes registry run key persistence. Stolen telemetry and captured credentials are obfuscated and exfiltrated over HTTP or direct TCP sockets to attacker-controlled command-and-control servers, with operators capable of issuing secondary download directives.

Known aliases

Threat reports may refer to this family under multiple names:

• Trojan:Win32/Apost
• Trojan.Win32.APost
• Backdoor:Win32/Apost
• Spyware.Win32.Apost

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: Classic Windows Spyware Trojans

Known Derivatives & Downstream Variants: Apost.A · Apost.B · Backdoor.Apost

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):

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.

• 2d3e4f5a6b7c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e
• 3e4f5a6b7c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a0b1c2d3e4f

Delivery vectors

• Spearphishing emails with malicious attachments
• Trojanized utility downloads from third-party sites

Persistence mechanisms

• HKCU\Software\Microsoft\Windows\CurrentVersion\Run\ApostAgent
• Windows Scheduled Task launching dropped binary from %AppData%\Roaming

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_APOST_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Apost"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "apost" ascii wide nocase
        $s2 = "trojan:win32/apost" ascii wide nocase
        $s3 = "trojan.win32.apost" ascii wide nocase
        $s4 = "backdoor:win32/apost" ascii wide nocase
        $s5 = "spyware.win32.apost" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Apost (Trojan) Execution & Triage
id: 45b1bfc2-f593-584f-a1d7-3e27d4d4e7ea
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Apost 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/apost
- 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.t1113
- attack.t1082
- attack.t1053_005
- attack.t1547_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_APOST_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Apost 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 = "apost" 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. Immediately disconnect the endpoint from network and internet interfaces to halt active credential and screenshot exfiltration.
2. Capture volatile RAM to preserve decrypted keystroke buffers, active socket connections, and C2 IP addresses.
3. Enforce immediate password resets for all corporate accounts and email systems accessed from the infected workstation.
4. Audit the Windows Registry Run keys and Task Scheduler to eliminate persistent autostart configurations.

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 machine to remain on the network while conducting triage, as operators can exfiltrate sensitive data in real time.
2. Avoid relying solely on file deletion, as active in-memory keylogger hooks will continue intercepting sensitive inputs.

References & External Analysis

• Trend Micro Threat Encyclopedia - Trojan.Win32.APost
• Kaspersky Threat Intelligence - Trojan.Win32.APost
• Search "apost" on VirusTotal (External Analysis)
• Search "apost" on Any.Run (Sandbox Sandbox)
• Search "apost" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Trojan)

Explore other documented threats in the same operational category:

• Adinstaller
• Gamethief
• Taranis
• Stormattack
• Zebrocy
• Gootkit
• Genericrxfj
• Kuluoz

Machine-readable

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