Intelligent App Control (IAC) Explained: Windows’ App Gatekeeper for Unknown Apps

What IAC is (and what it is not)

Intelligent App Control is a Windows feature that blocks execution of apps that don’t meet a “known good” bar. Think of it as an execution gate built around code integrity and reputation, not a scanner that hunts for known-bad patterns.

IAC is meant for consumer and small-to-medium environments first, but it shows up in enterprise conversations because it behaves like a simplified allowlisting control. It’s not a replacement for WDAC in tightly managed fleets. It’s not AppLocker with nicer marketing. And it’s definitely not “Defender but stricter.”

What IAC does

• Prevents unknown or untrusted executables from running based on policy and trust signals.
• Leans on code integrity and reputation to decide what’s acceptable.
• Reduces “first run” risk from downloaded tools, ad-hoc installers, and living-off-the-land style droppers that rely on arbitrary code execution.

What IAC does not do

• It does not “clean” malware. If something already ran and persisted, that’s a different game.
• It does not guarantee safety. Signed software can be malicious. Reputable software can become compromised. Attackers love supply chains.
• It does not replace patching and least privilege. It complements them.

Joke #1: Allowlisting is like a bouncer with a clipboard. It doesn’t stop fights inside the club, but it does stop most random strangers from walking in holding fireworks.

Why Microsoft shipped it: the threat model

Windows endpoints are still where most organizations bleed. Not because Windows is uniquely cursed, but because endpoints are where people click things, run things, and install things. Attackers don’t need elegance when they have invoices in PDF-shaped clothing.

IAC targets a brutally common failure mode: unknown code execution. Not “known malware,” not “detected malware,” but “some binary we’ve never seen before running with user context, and sometimes escalating.”

The problems IAC tries to shrink

• Drive-by installers that users run because a website told them to update a codec.
• Side-loaded payloads dropped by macros, script engines, or abused installers.
• Developer workstation drift where “temporary tools” become permanent supply-chain risk.
• Shadow IT in the form of random remote support tools and “free” PDF editors.

From an SRE perspective, IAC is Microsoft acknowledging that detection-only controls create too much mean time to innocence. Blocking unknown code at the door is sometimes the only way to keep the blast radius small enough to debug rationally.

How IAC decides: trust signals and the execution path

IAC is easiest to understand if you stop thinking “antivirus” and start thinking “execution policy.” The core question is not “is this malicious?” It’s “is this allowed to run?” That subtlety changes how you troubleshoot and how you design exceptions.

Decision inputs (the practical view)

• Code signing and certificate trust: Is the binary signed? Is the signer reputable? Is the chain valid?
• Reputation / cloud intelligence: Has Microsoft seen this file (or similar) widely and safely?
• Code integrity policy state: Are we in an enforced mode that blocks unknowns?
• Context: Some controls behave differently based on whether a file is downloaded (Mark-of-the-Web), its origin, or how it was launched.

What happens at runtime

When a process is created, Windows evaluates whether the image is permitted. In IAC-enabled scenarios, the system consults code integrity policy and associated intelligence to permit, block, or in some cases require elevation/approval pathways depending on configuration. If blocked, the user often sees a generic message that feels like SmartScreen, but the enforcement plumbing is closer to Windows Defender Application Control (WDAC) than to a browser prompt.

Why it “suddenly” starts happening

Most “it worked yesterday” incidents come down to one of these:

• A device moved into a state where IAC became active (fresh install, reset, new build).
• A line-of-business tool updated and its signing or packaging changed.
• A previously tolerated unsigned helper binary is now getting judged as unknown and blocked.
• SmartScreen was the visible face before; IAC becomes the enforcement behind it now.

IAC vs Defender vs SmartScreen vs WDAC vs AppLocker

This is where most teams get lost: these features overlap in user experience, but they live at different layers and answer different questions. If you mix them up, you’ll apply the wrong fix, then wonder why the block persists.

Defender Antivirus: “Is it malicious?”

Defender AV is primarily a detection and remediation engine. It scans files at rest and in motion, uses signatures, heuristics, behavior monitoring, and cloud intelligence to decide if something is malware. It can quarantine, remediate, and report. It is not fundamentally an allowlist.

Operational implication: if a binary is blocked by IAC, you can stare at Defender’s threat history all day and find nothing. That’s not a Defender bug. That’s you looking in the wrong drawer.

SmartScreen: “Do we trust this download or this publisher?”

SmartScreen is reputation-driven and often shows up at download or first-run time, especially for files with Mark-of-the-Web. It’s the Windows version of a skeptical friend asking, “Are you sure you got that from a normal place?” It can warn, block, or require extra clicks.

Key difference: SmartScreen is often a user prompt and a reputation check. IAC is a stronger policy posture that can become a hard block without “just click Run anyway.”

WDAC: “Is this code allowed to execute, period?”

Windows Defender Application Control is the enterprise-grade framework for code integrity allowlisting. WDAC policies can be extremely strict and extremely precise: allow signed Microsoft code, allow specific publishers, allow hashes for exact binaries, allow paths under certain protections, and so on.

Relationship: IAC is conceptually adjacent to WDAC. In practice, you should assume IAC enforcement and logging resemble code integrity behaviors more than antivirus behaviors.

AppLocker: “Can this user run this app?” (and “Which rules do we apply?”)

AppLocker is older, policy-based, and often deployed via Group Policy in domain environments. It can restrict executables, scripts, Windows Installer packages, and packaged apps using publisher/path/hash rules.

Key difference: AppLocker is rule-based and admin-managed. IAC is more opinionated and reputation-aware, designed to be “safe by default” without asking you to write 400 rules before lunch.

Where admins get burned

• They disable SmartScreen and think the problem is solved. IAC keeps blocking because it’s not SmartScreen.
• They add Defender exclusions for a folder. IAC still blocks because it’s not scanning; it’s enforcing execution policy.
• They create an AppLocker allow rule but the device isn’t using AppLocker for enforcement in that scenario. The user is still blocked.
• They deploy WDAC without a plan and accidentally stack enforcement with IAC-like postures. Then they blame “Windows.”

Interesting facts and history you can use in meetings

• Allowlisting predates modern AV hype. Enterprises were doing “approved software lists” long before ransomware made it fashionable.
• AppLocker arrived as a successor to Software Restriction Policies (SRP). SRP was effective but blunt; AppLocker added publisher rules and better management.
• Code Integrity is not new. Windows has enforced kernel-mode signing for years; user-mode code integrity controls expanded over time.
• SmartScreen’s origin story is reputation. It wasn’t designed to catch all malware; it was designed to warn on low-reputation downloads and phishing.
• WDAC used to be called Device Guard in many conversations. The naming evolved, the pain stayed familiar: “great security, now make it usable.”
• Mark-of-the-Web changed endpoint security. That little “downloaded from the internet” flag became a key input for Office macros, SmartScreen, and first-run warnings.
• Microsoft leaned harder into “default deny” after waves of commodity ransomware. The industry learned that detection-only is a tax you pay forever.
• Reputation systems have a bootstrapping problem. New internal apps are “unknown” by definition, which is why enterprise exception workflows matter.

Operating model: what changes in IT operations

IAC is not just a toggle; it’s a commitment to having an opinion about what software belongs on your endpoints. If your organization currently treats endpoints like personal laptops with email installed, you’re about to feel friction. Good friction, but friction.

The healthy mindset

• Standardize software distribution. The more you rely on “download and run,” the more IAC will feel like a constant incident.
• Prefer signed software from reputable publishers. If your internal tools are unsigned, you’re choosing pain.
• Build an exception process with telemetry. If you can’t answer “what was blocked, where, and why,” you’ll create cargo-cult exceptions.
• Design for updates. Allow rules that break every patch cycle are not security; they’re theater.

A reliability quote worth stapling to your change requests

Hope is not a strategy. — General Gordon R. Sullivan

Security posture is the same: you don’t “hope” users run only safe apps. You either enforce it or you don’t.

Practical tasks: commands, outputs, and decisions (12+)

These are the things I actually run when a machine starts blocking apps and the ticket is full of screenshots and emotions. Commands are written as if executed in a PowerShell-like environment, but shown in a generic shell prompt per your formatting requirement. Interpret the outputs; make a decision.

Task 1: Confirm the Windows build and edition (because features are gated)

cr0x@server:~$ systeminfo | findstr /B /C:"OS Name" /C:"OS Version"
OS Name:                   Microsoft Windows 11 Enterprise
OS Version:                10.0.22631 N/A Build 22631

What it means: You’re on Windows 11, recent build. IAC is in-scope depending on device state and configuration.

Decision: If this is Windows 10 or an older build, stop blaming IAC and pivot to WDAC/AppLocker/SmartScreen or plain AV policy.

Task 2: Check if Secure Boot is on (many modern protections assume it)

cr0x@server:~$ powershell -NoProfile -Command "Confirm-SecureBootUEFI"
True

What it means: Secure Boot is enabled; code integrity protections are in a good posture.

Decision: If False or errors (legacy BIOS), expect inconsistent enforcement and weaker guarantees. Document it; don’t “work around” it with exclusions.

Task 3: Check virtualization-based security status (VBS / HVCI context)

cr0x@server:~$ powershell -NoProfile -Command "Get-CimInstance -ClassName Win32_DeviceGuard | Select-Object -ExpandProperty SecurityServicesRunning"
1
2

What it means: Security services are running (values vary by system). Often indicates VBS/HVCI components are active.

Decision: If nothing is running, you may still have IAC behavior but fewer integrity guarantees. For strict environments, align baseline security features first.

Task 4: Query Windows Defender status (to separate AV blocks from IAC blocks)

cr0x@server:~$ powershell -NoProfile -Command "Get-MpComputerStatus | Select-Object AMServiceEnabled,AntivirusEnabled,RealTimeProtectionEnabled"
AMServiceEnabled          : True
AntivirusEnabled          : True
RealTimeProtectionEnabled : True

What it means: Defender is active. This does not prove Defender is blocking the app; it just confirms AV is in play.

Decision: If Defender is off due to third-party AV, your user may still see IAC blocks; don’t assume AV vendor is the cause.

Task 5: Check Defender threat history quickly (look for actual detections)

cr0x@server:~$ powershell -NoProfile -Command "Get-MpThreatDetection | Select-Object -First 3 ThreatName,ActionSuccess,InitialDetectionTime"
ThreatName                 ActionSuccess InitialDetectionTime
----------                 ------------- --------------------
Trojan:Win32/Wacatac.B!ml  True          1/18/2026 2:14:11 PM

What it means: Defender did detect something recently. This can co-exist with IAC but is a separate thread.

Decision: If there’s a relevant detection matching the blocked file path or hash, treat it as malware until proven otherwise. Don’t bypass controls to “get work done.”

Task 6: Inspect SmartScreen-related events (reputation prompts)

cr0x@server:~$ powershell -NoProfile -Command "Get-WinEvent -LogName 'Microsoft-Windows-SmartScreen/Debug' -MaxEvents 5 | Select-Object TimeCreated,Id,Message"
Get-WinEvent : The specified channel could not be found.

What it means: The SmartScreen debug channel may not exist/enabled on this host (common). Don’t get stuck here.

Decision: Pivot to Code Integrity and AppLocker logs; SmartScreen logging is not consistently available.

Task 7: Pull Code Integrity operational events (where IAC/WDAC-style blocks show up)

cr0x@server:~$ powershell -NoProfile -Command "Get-WinEvent -LogName 'Microsoft-Windows-CodeIntegrity/Operational' -MaxEvents 5 | Select-Object TimeCreated,Id,Message"
TimeCreated            Id Message
-----------            -- -------
2/5/2026 9:10:04 AM  3077 Code Integrity determined that a process (\Device\HarddiskVolume3\Users\sam\Downloads\tool.exe) attempted to load \Device\HarddiskVolume3\Users\sam\Downloads\tool.exe that did not meet the Store signing level requirements.

What it means: This is the money log. It indicates a code integrity decision blocked or constrained execution.

Decision: If you see the target binary path here, treat it as an allowlisting/integrity issue (IAC/WDAC), not an AV false positive.

Task 8: Check AppLocker event logs (in case it’s actually AppLocker)

cr0x@server:~$ powershell -NoProfile -Command "Get-WinEvent -LogName 'Microsoft-Windows-AppLocker/EXE and DLL' -MaxEvents 3 | Select-Object TimeCreated,Id,Message"
TimeCreated            Id Message
-----------            -- -------
2/5/2026 9:09:58 AM  8004 %SYSTEM32%\tool.exe was prevented from running.

What it means: AppLocker is actively blocking an EXE/DLL. Different fix path than IAC.

Decision: If AppLocker is the blocker, don’t waste time on IAC toggles. Review GPO rules and enforcement mode.

Task 9: See effective AppLocker policy (rule debugging)

cr0x@server:~$ powershell -NoProfile -Command "Get-AppLockerPolicy -Effective -Xml"

  
    
      ...
    
  

What it means: AppLocker rules are enabled and you can inspect the allow/deny model.

Decision: If the app’s publisher/path/hash doesn’t match an allow rule (or hits a deny), add a publisher rule where possible. Avoid hash rules unless you enjoy weekly maintenance.

Task 10: Check if the file has Mark-of-the-Web (MOTW) and came from the internet

cr0x@server:~$ powershell -NoProfile -Command "Get-Item -Path 'C:\Users\sam\Downloads\tool.exe' -Stream Zone.Identifier -ErrorAction SilentlyContinue | Format-List"
FileName : C:\Users\sam\Downloads\tool.exe:Zone.Identifier
Length   : 26

What it means: The file has a Zone.Identifier alternate data stream. SmartScreen and related reputation checks often trigger on first-run for MOTW files.

Decision: If this is a legitimate internal tool distributed via email or browser download, stop doing that. Move distribution to a managed channel (Intune/ConfigMgr, signed installer, internal repo).

Task 11: View the file’s Authenticode signature (signed vs unsigned reality)

cr0x@server:~$ powershell -NoProfile -Command "Get-AuthenticodeSignature -FilePath 'C:\Users\sam\Downloads\tool.exe' | Format-List"
SignerCertificate : 
Status            : NotSigned
StatusMessage     : The file is not digitally signed.

What it means: Unsigned binaries are the fastest way to become “unknown.” In IAC-like postures, unsigned often equals blocked.

Decision: For internal software, fix the pipeline: sign code, sign installers, and version artifacts. Don’t normalize “just unblock it.”

Task 12: Check the signer and certificate chain when it is signed

cr0x@server:~$ powershell -NoProfile -Command "Get-AuthenticodeSignature -FilePath 'C:\Program Files\Vendor\App\app.exe' | Select-Object Status,SignerCertificate | Format-List"
Status : Valid
SignerCertificate : [Subject]
  CN=Vendor LLC, O=Vendor LLC, L=Seattle, S=WA, C=US

What it means: The signature is valid and chained. Reputation may still be low, but you’re no longer dealing with “unsigned mystery meat.”

Decision: If signed but blocked, investigate reputation/allow rules; consider publisher-based allowlisting in WDAC/AppLocker rather than disabling controls.

Task 13: Identify what actually blocked execution (correlate by time)

cr0x@server:~$ powershell -NoProfile -Command "$t=(Get-Date).AddMinutes(-20); Get-WinEvent -FilterHashtable @{LogName='Microsoft-Windows-CodeIntegrity/Operational'; StartTime=$t} | Select-Object -First 10 TimeCreated,Id,Message"
TimeCreated            Id Message
-----------            -- -------
2/5/2026 9:10:04 AM  3077 Code Integrity determined that a process (...) attempted to load (...) that did not meet the Store signing level requirements.

What it means: You have a time-windowed view. It’s how you prove to stakeholders that it’s policy enforcement, not “Windows randomly hates us.”

Decision: Use these event IDs to build a detection/alerting view in your SIEM. If you don’t centralize this, you’ll keep debugging from screenshots.

Task 14: Check WDAC / code integrity policy files presence (when you suspect enterprise policies)

cr0x@server:~$ dir C:\Windows\System32\CodeIntegrity
Volume in drive C has no label.
Directory of C:\Windows\System32\CodeIntegrity

02/05/2026  09:01 AM    <DIR>          .
02/05/2026  09:01 AM    <DIR>          ..
01/20/2026  04:31 PM           245,760 SiPolicy.p7b

What it means: A code integrity policy file exists. That often indicates WDAC-style enforcement is configured, regardless of what the user thinks is enabled.

Decision: If you see policy artifacts, treat the environment as managed allowlisting. Coordinate changes through the policy owner; don’t try to “fix” on a single endpoint.

Task 15: Verify if the blocked binary is being launched from a user-writable location

cr0x@server:~$ powershell -NoProfile -Command "Test-Path 'C:\Users\sam\AppData\Local\Temp\tool.exe'"
True

What it means: The app is executing from Temp. That’s a classic malware tradecraft path, and modern controls distrust it.

Decision: Fix the installer or packaging. Legit software should not run primary executables from Temp long-term. Move to Program Files with proper signing.

Task 16: Confirm Group Policy application (if AppLocker policies are suspected)

cr0x@server:~$ gpresult /r
COMPUTER SETTINGS
------------------
Applied Group Policy Objects
-----------------------------
  Workstation Baseline
  App Control Policy

What it means: GPOs are applied that likely include app control rules.

Decision: If a new GPO recently rolled out, correlate change time to incident time. Roll back deliberately; don’t “just add everyone to local admins.”

Fast diagnosis playbook

If you only have ten minutes before a meeting turns into a blame festival, do this in order. The goal is to identify the enforcement layer, then the reason, then the smallest safe remediation.

1) Identify the enforcement layer (don’t guess)

1. Check Code Integrity operational log for block events and the file path.
2. Check AppLocker logs for explicit prevent events.
3. Check Defender threat detections for quarantines/detections.
4. Check MOTW and SmartScreen-like symptoms (downloaded file context).

Bottleneck you’re hunting: “Which subsystem said no?” Everything else is noise.

2) Determine why the binary is “unknown”

1. Is it unsigned?
2. Is it signed but from a new/low-reputation publisher?
3. Is it being executed from a user-writable directory like Downloads/Temp?
4. Did the app just update and change signing or packaging?

Bottleneck you’re hunting: trust signal failure (signature, reputation, location, policy mismatch).

3) Choose a remediation that doesn’t create future incidents

1. Best: distribute via managed software deployment + signed artifacts.
2. Acceptable: publisher-based allow rule (AppLocker/WDAC) for a stable vendor.
3. Last resort: hash allow rules for a specific binary version.
4. Do not: disable IAC/WDAC/SmartScreen across the fleet because one tool is blocked.

Joke #2: Turning off app control to run one tool is like removing the front door because a pizza box didn’t fit. It works, but you won’t like the follow-up.

Three corporate mini-stories from the trenches

Mini-story 1: The incident caused by a wrong assumption

A mid-sized finance company rolled out new Windows 11 laptops to a pilot group. Within two days, their internal “VPN helper” stopped launching. The helpdesk assumed Defender had quarantined it, because that’s the familiar storyline: “AV broke the app again.” They added a Defender folder exclusion for the tool’s directory and told users to retry.

It still failed. Same block prompt, same user rage. The escalation went to endpoint engineering, who spent half a day combing Defender logs, only to find nothing matching the file. The tool wasn’t being detected; it was being denied execution.

The breakthrough was boring: someone finally checked Code Integrity operational events and found the helper EXE was unsigned and running from the user’s Downloads folder because the “installer” was a self-extracting archive. On older builds, SmartScreen warnings were click-through and users got used to ignoring them. On the new build baseline, the system simply refused.

The fix wasn’t a bigger exclusion. They rebuilt the helper as a properly signed installer that placed binaries under Program Files and signed the executable with the company’s code-signing certificate. The incident ended, and so did the habit of distributing “installers” by sending zip files over email.

Mini-story 2: The optimization that backfired

A global manufacturing firm decided software packaging was “too slow.” They optimized the process by allowing teams to publish internal utilities to a shared file share and run them directly, no packaging, no signing, “because speed.” It worked for months, right up until it didn’t.

After an OS baseline refresh, a chunk of endpoints began blocking those utilities. Engineers tried the obvious: move the utilities to a different share, rename them, zip them, unzip them. Each workaround changed the symptom but not the underlying trust problem.

The quiet root cause: their “optimization” created a permanent stream of unknown binaries that were never signed and never distributed through a controlled channel. Reputation never had a chance. Policy enforcement eventually did its job. The environment wasn’t broken; it was finally consistent.

The eventual remediation was expensive in calendar time but cheap in incidents: they stood up a minimal internal packaging pipeline that signs binaries, versions them, and deploys via their endpoint management tool. The “fast” path had been generating a long tail of failure and operational chaos. They got their speed back, but in a way that didn’t require superstition and file renames.

Mini-story 3: The boring but correct practice that saved the day

A healthcare org had already lived through one ransomware event. Their response was not flashy. They created an app intake process: every new tool must be signed, assigned an owner, and distributed via managed deployment. Exceptions required a ticket, a business justification, and expiration.

When IAC-like blocking started appearing on newer Windows 11 devices, they didn’t panic. They already had the habit of checking the right logs and correlating block events with software distribution records.

One Friday afternoon, a vendor pushed an emergency hotfix that changed the signing chain on a small helper executable. A handful of endpoints blocked it. Instead of disabling protection, the team paused deployment, validated the new signature, updated their allow rules/publisher trust where appropriate, and resumed rollout. Users saw a short delay, not a week-long outage.

The “boring” parts—signing, ownership, telemetry, and staged rollout—meant the incident was a controlled change, not a production fire. That’s what mature endpoint operations looks like: less heroism, more receipts.

Common mistakes: symptoms → root cause → fix

1) “We added a Defender exclusion, but it’s still blocked.”

Symptom: App won’t run; Defender shows no detection; exclusions don’t help.

Root cause: It’s not an AV detection. It’s code integrity / allowlisting enforcement (IAC/WDAC/AppLocker).

Fix: Check CodeIntegrity and AppLocker logs. Move to signed artifacts and an allow rule model; do not expand AV exclusions.

2) “Disabling SmartScreen didn’t change anything.”

Symptom: Users still get blocked after SmartScreen is turned off via policy.

Root cause: SmartScreen prompts are not the enforcement layer; IAC/WDAC is blocking execution.

Fix: Confirm in CodeIntegrity operational log. If you need exceptions, implement them in WDAC/AppLocker or adjust the app distribution/signing.

3) “It only fails when launched from Downloads.”

Symptom: Same EXE runs from Program Files but not from Downloads/Temp.

Root cause: MOTW + user-writable path triggers stricter reputation/integrity posture.

Fix: Install correctly (signed installer to Program Files). Don’t train users to run business tools from Downloads.

4) “We allowed the hash, and it broke again after update.”

Symptom: After every vendor update, the app blocks again.

Root cause: Hash rules are version-specific; updates change hashes.

Fix: Use publisher rules (certificate-based) or package-based rules. Hash rules are a tactical bandage, not a strategy.

5) “Only some machines block it, others run it fine.”

Symptom: Inconsistent behavior across endpoints.

Root cause: Different baselines: Windows build, IAC state, Secure Boot/VBS, or different applied policies (GPO/MDM).

Fix: Compare baselines (OS build, gpresult, CodeIntegrity policy file presence). Standardize configuration before chasing ghosts.

6) “The app is signed, so why blocked?”

Symptom: Authenticode signature is valid but execution is denied.

Root cause: Signing is necessary, not sufficient. Reputation may be low; policy may require specific signing levels; chain might be acceptable but not allowed by rule.

Fix: Validate signer identity and chain. Prefer publisher allow rules for trusted vendors; ensure the vendor uses stable signing. For internal apps, sign with your enterprise certificate and manage trust properly.

7) “We fixed it by making users local admins.”

Symptom: Someone escalated privileges and the app ran (or appeared to).

Root cause: You changed the threat model, not the control. Also, many code integrity blocks don’t care about admin rights.

Fix: Roll back local admin sprawl. Fix distribution/signing/policy. Admin-by-default is how you get a breach with excellent time-to-click.

Checklists / step-by-step plan

Checklist A: When a user reports “IAC blocked my app”

1. Get the exact file path, filename, and timestamp of the block.
2. Pull CodeIntegrity operational events around that timestamp.
3. Pull AppLocker events (EXE and DLL log) around that timestamp.
4. Check Defender detections for the same timeframe (separate track).
5. Inspect the file signature (signed? valid? which publisher?).
6. Check MOTW (Zone.Identifier) for downloaded context.
7. Decide remediation: repackage/sign/distribute vs allow rule vs deny.

Checklist B: Building a sane exception workflow

1. Define “supported software” vs “user-installed.” Write it down. Enforce it.
2. Require an owner for each allowed app (team, not a person).
3. Prefer publisher trust (certificate) over hash and path.
4. Time-box exceptions with expiry and renewal.
5. Centralize logs: CodeIntegrity, AppLocker, Defender detections.
6. Staged rollouts: pilot, then rings, then broad deployment.
7. Require internal tools to be signed and built via CI/CD.

Checklist C: Designing internal apps to not get blocked

1. Sign executables and installers with a managed code-signing cert.
2. Install to Program Files; avoid living in Downloads/Temp.
3. Avoid self-extracting archives as “installers” unless you enjoy support tickets.
4. Version artifacts; don’t overwrite binaries in place on file shares.
5. Document update cadence and signing changes.
6. Test on a machine that matches your strictest baseline.

FAQ

1) Is Intelligent App Control the same as WDAC?

No. WDAC is the full enterprise framework for code integrity policies and allowlisting. IAC is a more opinionated “default deny unknown” posture that behaves WDAC-adjacent but aims to reduce admin rule-writing.

2) Is IAC the same as SmartScreen?

No. SmartScreen is primarily reputation prompting and warning behavior, often tied to downloads and first-run. IAC is enforcement that can block execution even when users would normally click through.

3) If IAC blocks an app, does that mean it’s malware?

Not automatically. It means the app didn’t meet the trust threshold (signature, reputation, policy). Treat it as suspicious until verified, but don’t equate “unknown” with “malicious.”

4) Why do my internal tools get blocked more than commercial software?

Because internal tools are often unsigned, distributed informally, and have low reputation. Commercial vendors usually sign consistently and have widespread reputation signals.

5) Can I just whitelist a folder like C:\Tools\ ?

You can, but you shouldn’t. Path-based allow rules for user-writable locations are how attackers turn your “tools folder” into their deployment platform. Prefer signed publisher rules and managed installation paths.

6) Why does it block only on new Windows 11 laptops?

New builds and fresh installs often have stricter defaults and different security baselines (Secure Boot, VBS, and policy posture). Your older machines may be drifting, not “working.” Standardize.

7) How do I prove to management what blocked the app?

Use event logs. CodeIntegrity operational events and AppLocker logs provide direct evidence with timestamps and file paths. Screenshots of popups are not evidence; they’re theater.

8) What’s the best long-term fix when a legitimate vendor app is blocked?

Get the vendor to provide properly signed binaries and stable signing practices. In parallel, implement publisher-based allow rules (where appropriate) and deploy through managed channels so updates don’t become random “unknowns.”

9) Does making the user a local admin bypass IAC?

Often no, and even when it changes behavior, it’s the wrong lever. Local admin sprawl increases your blast radius and makes incident response harder. Fix trust and distribution instead.

10) What should I monitor to catch this before it becomes a ticket storm?

Centralize and alert on CodeIntegrity operational block events and AppLocker prevent events. Trend them by binary signer, path, and device cohort to spot new breakage after updates or policy changes.

Conclusion: next steps that actually reduce risk

If you remember one thing: IAC is an execution gate. Don’t troubleshoot it like antivirus. Identify the enforcement layer, read the code integrity logs, and fix the trust problem—not the symptom.

Practical next steps:

1. Instrument: Start collecting CodeIntegrity and AppLocker logs centrally.
2. Standardize distribution: Stop “download and run” for business software. Package it.
3. Sign internal code: Make code signing part of the build, not a ritual performed during outages.
4. Prefer publisher-based allow rules: Hash rules are for emergencies, not normal operations.
5. Run staged rollouts: Let a pilot group catch reputation and signing surprises before the whole company does.

You don’t need to love IAC. You just need to operate it like a production control: measured, observable, and resistant to panic-driven exceptions.