Bsymem

Overview

Trojan:Win32/Bsymem (cataloged across vendor telemetry as Trojan.Bsymem or Ransom.Bsymem) is a stealthy dual-stage remote access backdoor and enterprise ransomware staging vehicle designed to establish persistent covert access within corporate environments. Delivered via targeted spear-phishing attachments or dropped through exploit kits, Bsymem utilizes multi-layer code packing and process injection into legitimate Windows services (such as svchost.exe) to conceal its outbound command-and-control communications. Once network persistence is secured via hidden scheduled tasks, Bsymem facilitates lateral network reconnaissance before executing a multi-threaded ransomware module that encrypts local and mapped network shares, terminates critical system services, and leaves ransom notes demanding cryptocurrency payments.

Known aliases

Threat reports may refer to this family under multiple names:

• Bsymem
• Trojan:Win32/Bsymem
• Trojan.Bsymem
• Win32/Bsymem
• Ransom.Bsymem
• Trojan:Win32/Bsymem.A

Threat Actor Attribution

Attribution is probabilistic, not a science. Each link below states its confidence level and the evidence behind it.

• Cybercrime Extortion Groups High confidence
  Basis:

Family Pedigree & Lineage

Malware authors regularly fork and iterate upon existing codebases. Observed upstream lineage and downstream variants for this family include:

Known Derivatives & Downstream Variants: Bsymem.A · Bsymem Svchost Injector · Bsymem Ransomware Payload Build

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:

• 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):

Exploited Vulnerabilities (CVEs)

This malware family is documented weaponizing the following common vulnerabilities and exposures:

• CVE-2017-11882 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).
• CVE-2017-0144 — In-depth exploitation analysis and catalog intelligence (NIST NVD ↗).

Command & Control (C2) and Network Profile

How this family talks to its operators. C2 traffic can often identify a family even when its code and configuration are hard to analyse. Ports and patterns are historical and change between campaigns, so use them as hunting leads rather than block-only rules.

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.

• 5b6c708192a3b4c5d6e7f8091a2b3c4d5e6f708192a3b4c5d6e7f81122334455
• c2d3e4f5a6b7c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d7e8f9a2334455

Delivery vectors

• spearphishing_attachments
• exploit_kit_payloads

Persistence mechanisms

• Windows Scheduled Task Creation
• svchost.exe process injection

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_BSYMEM_T1_ARTIFACT {
    meta:
        description = "Tier 1 Primitive Artifact: Raw string matches for Bsymem"
        tier = "T1 - Primitive Artifact"
        confidence = "Low-Medium (Fast Triage)"
        author = "SystemHelpdesk Threat Research Desk"
        date = "2026-10-14"
    strings:
        $s1 = "bsymem" ascii wide nocase
        $s2 = "bsymem" ascii wide nocase
        $s3 = "trojan:win32/bsymem" ascii wide nocase
        $s4 = "trojan.bsymem" ascii wide nocase
        $s5 = "win32/bsymem" ascii wide nocase
        $s6 = "ransom.bsymem" ascii wide nocase
        $s7 = "trojan:win32/bsymem.a" ascii wide nocase
    condition:
        uint16(0) == 0x5a4d and any of them
}

title: SystemHelpDesk Detection - Bsymem (Ransomware) Execution & Triage
id: 25dc1486-2810-530f-be92-2497bd283964
status: production
description: Detects execution, defense evasion, and persistence behaviors associated
  with the Bsymem malware family. Detects volume shadow copy deletion, boot status
  tampering, and recovery inhibition characteristic of modern ransomware operations.
references:
- https://malware-families-catalog.systemhelpdesk.com/families/bsymem
- https://malware-families-catalog.systemhelpdesk.com/defensive/ransomware-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.ransomware
- author.ricky-jordan
- source.systemhelpdesk-mfc
- attack.t1486
- attack.t1055
- attack.t1053_005
- attack.t1027
- attack.t1071_001
logsource:
  category: process_creation
  product: windows
detection:
  selection_process:
    Image|endswith:
    - \vssadmin.exe
    - \wmic.exe
    - \wbadmin.exe
    - \bcdedit.exe
    CommandLine|contains:
    - delete shadows
    - shadowcopy delete
    - resize shadowstorage
    - recoveryenabled no
    - ignoreallfailures
  condition: selection_process
falsepositives:
- Legitimate enterprise administrative scripts during approved change windows
- Authorized IT software deployment utilities and backup management agents
level: critical

rule MALWARE_WIN_BSYMEM_T3_ATTRIBUTION {
    meta:
        description = "Tier 3 Attribution Fingerprint: Heuristic detection for Bsymem 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 = "bsymem" 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 isolate infected endpoints from corporate subnets to halt active network share encryption.
2. Capture volatile RAM dumps before system shutdown to preserve unencrypted ransomware keys.
3. Audit scheduled tasks and remove unauthorized entries executing binaries from user AppData directories.
4. Deploy security updates patching Microsoft Office CVE-2017-11882 and SMB vulnerability MS17-010.

What to Avoid

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

1. Do not pay extortion ransom demands, as payment finances crime syndicates with no recovery guarantee.
2. Avoid allowing uninspected process injections into standard Windows services like svchost.exe.
3. Never leave unsegmented enterprise file shares accessible to all internal user subnets.

References & External Analysis

• Microsoft Security Intelligence: Trojan:Win32/Bsymem Threat Advisory
• Trend Micro Security Intelligence: Ransom.Bsymem Analysis
• NIST National Vulnerability Database CVE-2017-11882
• Search "bsymem" on VirusTotal (External Analysis)
• Search "bsymem" on Any.Run (Sandbox Sandbox)
• Search "bsymem" on MalwareBazaar (Malware Samples)

Frequently Asked Questions

Related Threats (Category: Ransomware)

Explore other documented threats in the same operational category:

• Idlekms
• Isnev
• Epack
• Magni
• Tgrandongc
• Upkm
• Malushka
• Systex

Machine-readable

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