Is BoundaryFill.aex safe?
Unsigned DLL with one tier-1 detection and T1055 process-injection evidence but no family consensus.
One tier-1 engine flagged the file as Trojan:Win32/Wacatac.B!ml while 70 others did not. The sample is unsigned, newly submitted, and triggered a process-injection heuristic, yet the sandbox returned no malicious verdict.
b99380026100ce1b40…81ae8938c180bbRecommended next actions
Before opening
Do not open it until the source can be verified independently.
If you already opened it
Stop using it, scan the device, and watch for unexpected behavior or security alerts. Get a fresh copy from the original trusted source and verify its exact hash when possible.
Intelligence
The saved assessment, checked against the scan evidence and recorded coverage.
The reasoning behind this verdict
This section explains the evidence supporting the verdict and keeps conflicting or missing signals visible.
One tier-1 engine flagged the file as Trojan:Win32/Wacatac.B!ml while 70 others did not. The sample is unsigned, newly submitted, and triggered a process-injection heuristic, yet the sandbox returned no malicious verdict.
The single Microsoft detection is the only malicious signal from 75 engines. The file is unsigned and rare_new, increasing uncertainty. Sandbox execution produced T1055 mapping but explicitly notes lack of proven intent, and no external intelligence sources corroborate malice.
What We Detected
Microsoft flagged the DLL as Trojan:Win32/Wacatac.B!ml; 70 of 75 engines returned clean. The file is an unsigned 64-bit DLL first seen today.
Threat Behavior
One sandbox run recorded T1055 process-injection activity via rundll32, yet the sandbox verdict was clean and only ambient WerFault files were written.
What To Do Now
Keep antivirus enabled. Do not execute the file until further samples or signatures appear. Monitor vendor updates for additional detections.
Where this verdict could be wrong3 caveats
- Single tier-1 detection with no family consensus and 70/75 undetected engines suggests possible false positive.
- Sandbox produced no malicious verdict and only ambient file writes typical of WerFault error reporting.
- No external-intel corroboration from CIRCL, MalwareBazaar or YARAify.
These are the assessment's weak points. If you believe one applies to your file, report the verdict and we'll re-review it.
- 70/75 engines undetected
- No sandbox malicious verdict
- No external intelligence hits
- Unsigned Win32 DLL
- Rare and newly submitted
- Single tier-1 malicious detection
- Process-injection heuristic triggered
Treat as suspicious pending additional samples or signatures; keep protection enabled and avoid execution.
Coverage & freshness
Complete means the check returned a usable result. It does not mean the file is safe.
Antivirus
Complete1 of 75 engines flagged the file.
Sandbox
Complete1 isolated runtime environment contributed observations.
Network
Not runNo contacted-host reputation check is recorded.
No timestamp recordedYARA
Complete1 signature or behavior rule matched.
External intel
PartialIndependent reference checks were attempted but are incomplete.
Behavior
Plain-English impact first, then the observed runtime evidence.
Runtime flight recorder
Capture complete- 1isolated sandbox run
- 6MITRE ATT&CK techniques
- 2spawned processes
- 0network contacts
- 5filesystem & mutex artifacts
What this file does
Observed actions and their security significance
High concern: Injected code into another process, a technique that can conceal execution.
High concern: Manipulated how the operating system loads code, which can redirect execution.
Moderate concern: Contained obfuscated or packed code that makes inspection harder.
Note: Reads your Windows user-account details.
Note: Collects details about your system.
These are observed capabilities from an isolated analysis. A technique does not prove malicious intent on its own, and the file never ran on your device.
Attack story
Runtime observations grouped by analysis stage. Arrows organize the stages; they do not claim chronology or causality.
Input file
The submitted object
- FileObserved
BoundaryFill.aex
b99380026100ce1b405a99ca341c08f87417170ba0ec4500ea81ae8938c180bb
01Uploaded file
Processes
Runtime execution
- ProcessObserved
Observed process
"C:\Windows\sysnative\rundll32.exe" "C:\Users\<USER>\Desktop\init.dll",#1
02Isolated runtime analysis - ProcessObserved
Observed process
C:\Windows\system32\WerFault.exe -u -p 3340 -s 588
03Isolated runtime analysis - +1 more recorded observation in Analyst mode
Files
Created or changed
- Written fileObserved
Temp
C:\ProgramData\Microsoft\Windows\WER\Temp
04Isolated runtime analysis - Written fileObserved
899112b4-8a69-423d-8d54-f67a1a6b27b8
C:\ProgramData\Microsoft\Windows\WER\Temp\899112b4-8a69-423d-8d54-f67a1a6b27b8
05Isolated runtime analysis - +1 more recorded observation in Analyst mode
5 recorded facts from one runtime window. Every fact remains independently traceable in Analyst mode.
What this file did when executed
This file was detonated in 1 sandbox and its runtime behaviour was observed.
Adversary techniques mapped to the MITRE ATT&CK framework.
- C:\ProgramData\Microsoft\Windows\WER\Temp
- C:\ProgramData\Microsoft\Windows\WER\Temp\899112b4-8a69-423d-8d54-f67a1a6b27b8
- C:\ProgramData\Microsoft\Windows\WER\ReportQueue
- C:\ProgramData\Microsoft\Windows\WER\Temp\520279ab-878d-4752-9ae3-d11dd5fb45b2
- C:\ProgramData\Microsoft\Windows\WER\ReportArchive
Detection & Forensics
Consensus, attribution, signatures, code structure, prevalence, and identity.
Evidence integrity
Chain of custody for the facts preserved in this report.
- 1rule hit recorded
- 1 / 75engines flagged
- 2sources in submission history
Why these facts are shown
Each statement identifies whether it was directly recorded or derived from saved scan facts.
- 01
1 high-confidence signature or behavior rule matched this file.
Verdict inputView chapterProvenanceDerivedSourceSignature and behavior rulesObserved at - 02
1 of 75 antivirus engines flagged the file, including Microsoft.
Verdict inputView chapterProvenanceObservedSourceAntivirus analysisObserved at - 03
The hash has been submitted 4 times from 2 sources.
ProvenanceDerivedSourceSaved report factsObserved at - 04
Scanned file: BoundaryFill.aex — b99380026100ce1b405a99ca341c08f87417170ba0ec4500ea81ae8938c180bb
ProvenanceObservedSourceUploaded fileObserved at - 05
Observed process — "C:\Windows\sysnative\rundll32.exe" "C:\Users\<USER>\Desktop\init.dll",#1
ProvenanceObservedSourceIsolated runtime analysisObserved at - 06
Observed process — C:\Windows\system32\WerFault.exe -u -p 3340 -s 588
ProvenanceObservedSourceIsolated runtime analysisObserved at - 07
File written: Temp — C:\ProgramData\Microsoft\Windows\WER\Temp
ProvenanceObservedSourceIsolated runtime analysisObserved at - 08
File written: 899112b4-8a69-423d-8d54-f67a1a6b27b8 — C:\ProgramData\Microsoft\Windows\WER\Temp\899112b4-8a69-423d-8d54-f67a1a6b27b8
ProvenanceObservedSourceIsolated runtime analysisObserved at
Detection sources at a glance
The available sources did not agree on a named threat category.
Available reference checks returned no match, but at least one source was unavailable. This is not a clean result.
Signatures and behavior heuristics
A community signature or high-severity behavioral heuristic matched. Signatures identify known patterns; heuristics are strong leads but are not proof on their own.
The saved runtime evidence maps this activity to MITRE T1055 (Process Injection). The mapping supports possible process injection, but it does not prove the exact injection method or the operator's intent.
Evidence"C:\Windows\sysnative\rundll32.exe" "C:\Users\<USER>\Desktop\init.dll",#1
1 of 75 engines flagged this file
View all 75 engine results
Section entropy & packers
No high-entropy executable section or known packer signature was detected. Data and resource sections can still have high entropy without indicating packed code.
How widely this file has been seen
Barely seen in the wild and first surfaced recently. 1 antivirus detection make that low prevalence materially relevant, but rarity alone is not proof of malware.
Fingerprint and provenance
- File name
- BoundaryFill.aex
- Format
- Win32 DLL
- Code signing
- No verified publisher
- Size
- 5.1 MB
- Last analyzed
- Aug 1, 2026, 9:54 AM UTC
b99380026100ce1b405a99ca341c08f87417170ba0ec4500ea81ae8938c180bbSafety & FAQ
Complete recovery guidance and answers for the next decision.
What to do now
We couldn't fully clear this file. Treat it with caution.
- Recovery step 01
Don't open it unless you're certain it came from a source you trust.
- Recovery step 02
Check where you got it — an unexpected attachment or a random download link is a red flag.
- Recovery step 03
If its origin cannot be confirmed, delete this file and use a fresh copy from a trusted source. Get a fresh copy from the original trusted source and verify its exact hash when possible.
- Recovery step 04
If you're still unsure, scan it again in a day or two — detections often catch up on newer files.
Safety FAQ
Direct answers grounded in the saved verdict and evidence in this report.
Is BoundaryFill.aex safe, or is it malware?
What is BoundaryFill.aex?
How many antivirus engines detected BoundaryFill.aex?
What should I do if I already opened BoundaryFill.aex?
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Community
Member reviews and reports for this exact file hash.