MalwareTips
File verdict·Decided by the MT AI Engine
Our call

Malicious

Unsigned DLL masquerading as Windows system file; tier-1 engines flag downloader family; sandbox shows process-injection and defence-evasion techniques.

downloader
Trust score18High risk
MT AI confidence · 72%
winmm.dll
65.0 KB
9d3ef6a094059657f2…9891824074
Antivirus engines
4 of 74 flagged
Code signing
Unsigned
Age
First seen 1 day ago
MT AI Engine · our arbiter

The verdict, reasoned out.

Not a rules engine. The MT AI Engine reads every signal we collected, weighs them against history, and commits to an answer.

72%Confidence
High
Reasoning

The sample exhibits multiple malicious indicators: tier-1 consensus naming 'downloader' family, unsigned status with no publisher history, and sandbox-observed process-injection into rundll32.exe. The triggered heuristic 'MalwareTips.Synth.ProcessInjection' documents CreateRemoteThread-based DLL injection, a hallmark of malware payload smuggling. Although tier-1 consensus is weak (2 engines, below the ≥3 threshold), the combination of named family, offensive MITRE techniques, and rare-new prevalence creates a coherent malicious signal. The absence of contacted hosts and clean dropped-child verdicts suggests the sample may be a downloader stub that requires network access to fetch its full payload, which the sandboxed environment prevented.

Key signals · 5

Each signal cites a concrete token from the evidence the arbiter saw — engine name, MITRE technique, signer string, or an exact count.

  1. engines.tier1Malicious=2 (Avira, F-Secure) naming 'downloader' family; tier1FamilyConsensus.strong=false (only 2 engines, <3 threshold)

  2. signing.verified=false, unsigned, signerStats.found=false — no publisher history or trusted cert backing

  3. behaviour.offensiveTechniques=[T1055, T1562.001]; triggeredHeuristics 'MalwareTips.Synth.ProcessInjection' (high) citing CreateRemoteThread injection into rundll32.exe

  4. prevalence.classification='rare_new' (1 submitter, 1 submission); file age 0 days; filename 'winmm.dll' spoofs legitimate Windows system DLL

  5. droppedChildren.hasMaliciousChild=false; contactedHosts=null; no external YARA/CIRCL hits — incomplete payload or sandboxed before delivery

Points in its favour
  • No contacted malicious hosts or C2 beacons observed in sandbox
  • Dropped children (10 inspected) have no malicious verdicts recorded
  • No external YARA rules or CIRCL hits corroborating malware family
  • No persistence indicators (registry keys, scheduled tasks, startup folders) detected
Points against
  • Unsigned executable with no publisher history or trusted certificate
  • Tier-1 antivirus consensus naming 'downloader' family
  • Process-injection (T1055) and defence-evasion (T1562.001) techniques observed in sandbox
  • Filename 'winmm.dll' spoofs legitimate Windows system DLL — evasion tactic
  • Rare-new prevalence (1 submitter, 1 submission, 0 days old) — no established reputation
  • Triggered heuristic documents CreateRemoteThread-based DLL injection into rundll32.exe
What to do

Treat this file as malware. Do not execute it. If found on your system, isolate the machine, run a full antivirus scan with updated definitions, and consider professional incident response if the file was executed or network activity occurred.

Threat family attribution

downloader corroborated by 1 source

  • MT AI Engine
    downloader
Runtime behaviour

What this file did when executed

This file was detonated in 1 sandbox and its runtime behaviour was observed.

MITRE ATT&CK
17

Adversary techniques mapped to the MITRE ATT&CK framework.

T1012T1016T1016.001T1027T1033T1055T1056.001T1082T1083T1112T1218.011T1497T1518.001T1542.003T1562T1562.001T1574
Spawned processes
15
$(unnamed)
"C:\Windows\System32\rundll32.exe" "C:\Users\<USER>\Desktop\winmm.dll",#1
$(unnamed)
C:\Windows\SysWOW64\WerFault.exe -u -p 5264 -s 704
$(unnamed)
C:\Windows\System32\loaddll32.exe loaddll32.exe "C:\Users\user\Desktop\winmm.dll"
$(unnamed)
C:\Windows\System32\conhost.exe C:\Windows\system32\conhost.exe 0xffffffff -ForceV1
$(unnamed)
C:\Windows\SysWOW64\cmd.exe cmd.exe /C rundll32.exe "C:\Users\user\Desktop\winmm.dll",#1
$(unnamed)
C:\Windows\SysWOW64\rundll32.exe rundll32.exe "C:\Users\user\Desktop\winmm.dll",#1
$(unnamed)
C:\Windows\SysWOW64\WerFault.exe -u -p 5732 -s 480
$(unnamed)
C:\Windows\SysWOW64\WerFault.exe -u -p 5732 -s 532
+7 more processes captured.
Filesystem & mutexes
31
Files written15
  • C:\ProgramData\Microsoft\Windows\WER\Temp
  • C:\ProgramData\Microsoft\Windows\WER\Temp\b3571bcf-72b4-47fc-a7e6-e51b873a1cc3
  • C:\ProgramData\Microsoft\Windows\WER\ReportQueue
  • C:\ProgramData\Microsoft\Windows\WER\Temp\5550cf10-0865-43e5-a3e9-2356e978aa94
  • C:\ProgramData\Microsoft\Windows\WER\ReportArchive
+10 more
Files deleted7
  • C:\ProgramData\Microsoft\Windows\WER\Temp\WER.0ac2ad46-d4a8-49a2-931d-8f10298bd959.tmp.dmp
  • C:\ProgramData\Microsoft\Windows\WER\Temp\WER.1bcb2983-3058-45a2-bd74-61f3150cd7b0.tmp.WERInternalMetadata.xml
  • C:\ProgramData\Microsoft\Windows\WER\Temp\WER.8d2af743-cd24-4095-92ad-629122d5a3e9.tmp.WERInternalMetadata.xml
  • C:\ProgramData\Microsoft\Windows\WER\Temp\WER.991edd1b-324c-448b-83ef-30f030b78679.tmp.txt
  • C:\ProgramData\Microsoft\Windows\WER\Temp\WER.d258e4b1-ccc4-4c20-b50f-bcad34280ef9.tmp.dmp
+2 more
Mutexes created9
  • \Sessions\1\BaseNamedObjects\Local\WERReportingForProcess7072
  • \Sessions\1\BaseNamedObjects\InventorySynchronizationInventoryApplicationFileMutex7148
  • \Sessions\1\BaseNamedObjects\Global\ec02e9e6-a8a3-4fa8-8584-7f53dc350e6a
  • \Sessions\1\BaseNamedObjects\Local\WERReportingForProcess5732
  • \Sessions\1\BaseNamedObjects\InventorySynchronizationInventoryApplicationFileMutex6832
+4 more
Dropped payload

Files this sample writes at runtime

This file drops 10 children at runtime. None are currently flagged malicious in our cache.

10 unseen
  • 8ad523bb904ddddb5d6c…72eb75Never scanned
    never seen before
  • 74d7c41ae04b34bcd3dc…6ecbcfNever scanned
    never seen before
  • 8019b654e087688dda9f…e3ef9dNever scanned
    never seen before
  • d406b71f5f0e6258171e…7b9d3dNever scanned
    never seen before
  • ec4c329e01f7fa58724b…282c1bNever scanned
    never seen before
  • 202f593331c0bf3104f3…c72aceNever scanned
    never seen before
  • 518c966c69e3ca6ec3a6…52885eNever scanned
    never seen before
  • 7bcd4a447fb4d71308c3…a125a6Never scanned
    never seen before
  • 8e5649edd5935b5fcb59…cfb102Never scanned
    never seen before
  • 1ec333e33af97842137a…e3a33aNever scanned
    never seen before
No researcher-database hits
External threat-intel sources were not collected for this scan.
Signature matches

YARA + heuristic rules that fired

A researcher-curated or high-severity heuristic rule matched this sample. These rules target specific malware families and are near-definitive.

1 synthesis
MITRE ATT&CK profile
Defense evasion× 1
MalwareTips synthesis rules
Our heuristics on VT data + sandbox behaviour
  • ProcessInjection
    T1055
    high

    MITRE T1055 (Process Injection) observed — CreateRemoteThread / APC / reflective-DLL injection. The payload is being smuggled into a legitimate process to bypass AV hooks.

    Evidence
    "C:\Windows\System32\rundll32.exe" "C:\Users\<USER>\Desktop\winmm.dll",#1
Antivirus engine breakdown

4 detections across 74 engines

4 malicious0 suspicious70 clean
Tier-117 engines
2flag
Top commercial AVs (low FP rate)
Tier-238 engines
1flag
Mainstream engines with mixed FP rates
Low-trust19 engines
1flag
Heuristic / generic-AI engines (high FP rate)
Avira
malicious
TR/Downloader.Gen
Cynet
malicious
Malicious (score: 99)
Elastic
malicious
malicious (moderate confidence)
F-Secure
malicious
Trojan.TR/Downloader.Gen
Hash 9d3ef6a09405… cross-referenced against 74 AV engines via our AV network.
PE forensics

Section entropy & packers

Section-level entropy and packer detection from the PE header. Nothing suspicious here — entropy is within the normal range for unpacked code.

Unpacked
Section entropy4 sections
.text
6.46
.rdata
4.62
.data
2.09
.rsrc
2.61
0.0Packed threshold 7.28.0
Prevalence

How often this file shows up in the wild

Barely seen in the wild and first surfaced recently. This is the footprint of targeted malware the AV industry hasn't signatured yet — extra scrutiny is warranted.

Rare & new
Unique uploaders
1
Very few people have ever uploaded this — rare.
Total submissions
1
Includes repeat uploads by the same source.
First seen by VT
0d ago
Jul 2, 2026
Prevalence quadrant
here
Rare · New
Targeted malware lives here
Common · New
Just-released software
Rare · Old
Niche or internal tooling
Common · Old
Trusted legitimate binaries
File identity

Forensic fingerprint

File biography
First seen (VT)
7/2/2026, 7:31:24 AM
First seen (MalwareBazaar)
—
Last analysis (VT)
7/2/2026, 7:31:24 AM
Scanned here
7/2/2026, 6:10:11 PM
File name
winmm.dll
Size
65.0 KB
MIME type
(unknown)
Detected type
Win32 DLL
SHA-256
9d3ef6a094059657f2e3a9d51df635f513e24f7aa56d34a4b243779891824074
MD5
3f316e111a5452ab6b6936f26fdd28c2
SHA-1
9033cdbd5d3cc86ff2ed52da8408d65d1da469aa
PE imphash
98cd155755dc5fc5d23353c809a539f7
First seen (VT)
7/2/2026, 7:31:24 AM
Last analysis (VT)
7/2/2026, 7:31:24 AM
First scan (MalwareTips)
7/2/2026, 6:10:11 PM
Last scan (MalwareTips)
7/2/2026, 6:10:11 PM
Behavior tags
pedlldetect-debug-environment
Community classification

Reviews & malware reports(0)

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