Go-Based Ransomware Sample Triggering High-Confidence Detections


Zero‑Dwell Threat Intelligence Report

A narrative, executive‑ready view into the malware’s behavior, exposure, and reliable defenses.
Generated: 2025-12-30 07:35:49 UTC

Executive Overview — What We’re Dealing With

This specimen has persisted long enough to matter. Human experts classified it as Malware, and the telemetry confirms a capable, evasive Trojan with real impact potential.

File
fcvn6.exe
Type
Win64 Executable (generic)
SHA‑1
e6e3eaf16a57d664c209fe1c9fe6cf7cfd69c9e0
MD5
ff2097ff942acf13461b7989f4f9eba9
First Seen
2025-12-29 12:35:03.026355
Last Analysis
2025-12-29 12:40:10.414200
Dwell Time
0 days, 7 hours, 33 minutes

Extended Dwell Time Impact

For 5+ minutes, this malware was rapidly detected — demonstrating excellent security controls that intercepted the threat during initial execution phases, severely limiting adversary capabilities.

Comparative Context

Industry studies report a median dwell time closer to 21–24 days. This case represents extremely rapid detection within minutes.

Timeline

Time (UTC) Event Elapsed
2025-10-23 12:56:16 UTC First VirusTotal submission
2025-12-30 05:11:39 UTC Latest analysis snapshot 67 days, 16 hours, 15 minutes
2025-12-30 07:35:49 UTC Report generation time 67 days, 18 hours, 39 minutes

Why It Matters

Every additional day of dwell time is not just an abstract number — it is attacker opportunity. Each day equates to more time for lateral movement, stealth persistence, and intelligence gathering.

Global Detection Posture — Who Caught It, Who Missed It

VirusTotal engines: 65. Detected as malicious: 43. Missed: 22. Coverage: 66.2%.

Detected Vendors

  • Xcitium
  • +42 additional vendors (names not provided)

List includes Xcitium plus an additional 42 vendors per the provided summary.

Missed Vendors

  • Acronis
  • Antiy-AVL
  • APEX
  • Baidu
  • Bkav
  • CMC
  • DrWeb
  • google_safebrowsing
  • huorong
  • Jiangmin
  • NANO-Antivirus
  • SentinelOne
  • SUPERAntiSpyware
  • TACHYON
  • tehtris
  • Trapmine
  • VBA32
  • VirIT
  • Webroot
  • Yandex
  • ZoneAlarm
  • Zoner

Why it matters: if any endpoint relies solely on a missed engine, this malware can operate with zero alerts. Prevention‑first controls close that gap regardless of signature lag.

Behavioral Storyline — How the Malware Operates

Dominant system-level operations (68.93% of behavior) suggest this malware performs deep system reconnaissance, privilege escalation, or core OS manipulation. It’s actively probing system defenses and attempting to gain administrative control.

Behavior Categories (weighted)

Weight values represent the frequency and intensity of malware interactions with specific system components. Higher weights indicate more aggressive targeting of that category. Each operation (registry access, file modification, network connection, etc.) contributes to the category’s total weight, providing a quantitative measure of the malware’s behavioral focus.

Category Weight Percentage
System 142 68.93%
Registry 29 14.08%
Process 13 6.31%
File System 10 4.85%
Misc 6 2.91%
Threading 3 1.46%
Device 2 0.97%
Network 1 0.49%

MITRE ATT&CK Mapping

  • T1071 – Binary file triggered YARA rule
  • T1027 – The binary likely contains encrypted or compressed data
  • T1027 – The binary contains an unknown PE section name indicative of packing
  • T1027.002 – The binary likely contains encrypted or compressed data
  • T1027.002 – The binary contains an unknown PE section name indicative of packing
  • T1027.002 – PE file has section (not .text) which is very likely to contain packed code (zlib compression ratio < 0.011)

Following the Trail — Network & DNS Activity

Outbound activity leans on reputable infrastructure (e.g., CDNs, cloud endpoints) to blend in. TLS sessions and
HTTP calls show routine beaconing and IP‑lookup behavior that can masquerade as normal browsing.

Contacted Domains

Domain IP Country ASN/Org
www.msftncsi.com 23.44.129.57 United States Akamai Technologies, Inc.

Observed IPs

IP Country ASN/Org
224.0.0.252
239.255.255.250
8.8.4.4 United States Google LLC
8.8.8.8 United States Google LLC

DNS Queries

Request Type
5isohu.com A
www.msftncsi.com A

Contacted IPs

IP Country ASN/Org
224.0.0.252
239.255.255.250
8.8.4.4 United States Google LLC
8.8.8.8 United States Google LLC

Port Distribution

Port Count Protocols
137 1 udp
5355 5 udp
53 4 udp
3702 1 udp

UDP Packets

Source IP Dest IP Sport Dport Time Proto
192.168.56.13 192.168.56.255 137 137 3.2442309856414795 udp
192.168.56.13 224.0.0.252 49311 5355 5.715475082397461 udp
192.168.56.13 224.0.0.252 55150 5355 3.1727499961853027 udp
192.168.56.13 224.0.0.252 60010 5355 5.385768175125122 udp
192.168.56.13 224.0.0.252 62406 5355 3.1750330924987793 udp
192.168.56.13 224.0.0.252 63527 5355 3.929004192352295 udp
192.168.56.13 239.255.255.250 52252 3702 3.188983201980591 udp
192.168.56.13 8.8.4.4 54879 53 8.02527117729187 udp
192.168.56.13 8.8.4.4 54881 53 6.6972761154174805 udp
192.168.56.13 8.8.8.8 54879 53 9.025285005569458 udp
192.168.56.13 8.8.8.8 54881 53 7.69746208190918 udp

Hunting tip: alert on unknown binaries initiating TLS to IP‑lookup services or unusual CDN endpoints — especially early in execution.

Persistence & Policy — Registry and Services

Registry and service telemetry points to policy awareness and environment reconnaissance rather than noisy persistence. Below is a compact view of the most relevant keys and handles; expand to see the full lists where available.

Registry Opened

31

Registry Set

0

Services Started

0

Services Opened

0

Registry Opened (Top 25)

Key
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Lsa\SspiCache\credssp.dll\RpcId
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\SecurityProviders\SecurityProviders
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Lsa\FipsAlgorithmPolicy\STE
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Lsa\FipsAlgorithmPolicy
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Lsa\SspiCache\credssp.dll\Name
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Lsa\SspiCache\credssp.dll\Capabilities
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Lsa\SspiCache\credssp.dll\Version
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Lsa\SspiCache\credssp.dll\Comment
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Lsa\SspiCache\credssp.dll\TokenSize
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Lsa\SspiCache\credssp.dll\Type
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Lsa\FipsAlgorithmPolicy\MDMEnabled
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Lsa\SspiCache\credssp.dll
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Lsa\FipsAlgorithmPolicy\Enabled
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\SdbUpdates
HKEY_LOCAL_MACHINE\Software\Microsoft\Rpc
HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\Safer\CodeIdentifiers
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\819168_win64_encrypt.exe
HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\MUI\Settings
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags\SdbUpdates\ManifestedMergeStubSdbs
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags
HKEY_LOCAL_MACHINE\OSDATA\Software\Microsoft\Windows NT\CurrentVersion\AppCompatFlags
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\AppModel\Lookaside\machine
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Image File Execution Options
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Shell Folders
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager
HKEY_LOCAL_MACHINE\System\Setup
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\AppModel\Lookaside\user
HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows NT\Rpc
HKEY_LOCAL_MACHINE\Software\Microsoft\LanguageOverlay\OverlayPackages\en-US
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Segment Heap
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Policies\Microsoft\Cryptography\Configuration
Show all (31 total)

Registry Set (Top 25)

Services Started (Top 15)

Services Opened (Top 15)

What To Do Now — Practical Defense Playbook

  • Contain unknowns: block first‑run binaries by default — signatures catch up, containment works now.
  • EDR controls: alert on keyboard hooks, screen capture APIs, VM/sandbox checks, and command‑shell launches.
  • Registry watch: flag queries/sets under policy paths (e.g., …\FipsAlgorithmPolicy\*).
  • Network rules: inspect outbound TLS to IP‑lookup services and unexpected CDN endpoints.
  • Hunt broadly: sweep endpoints for the indicators above and quarantine positives immediately.

Dwell time equals attacker opportunity. Reducing execution privileges and egress shrinks that window even when vendors disagree.

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