article IIS Application Pools Crash When OneAgent Deep Monitoring Is Enabled (ConfuserEx Obfuscation) in Troubleshooting https://community.dynatrace.com/t5/Troubleshooting/IIS-Application-Pools-Crash-When-OneAgent-Deep-Monitoring-Is/ta-p/292795 <DIV class="lia-message-template-content-zone"> <DIV> <DIV class="lia-message-template-content-zone"> <H2>Summary</H2> <DIV>This community article applies to Dynatrace OneAgent for Windows /.NET running on <STRONG>Microsoft IIS</STRONG> with <STRONG>deep monitoring</STRONG> enabled. It helps you diagnose and resolve <STRONG>IIS application pool crashes</STRONG> that occur because the application is <STRONG>obfuscated </STRONG>with ConfuserEx or a similar tool, which includes protection that terminates the process when a instrumentation is detected.</DIV> <DIV>&nbsp;</DIV> <H2>Problem</H2> <UL> <LI><STRONG>IIS application pools crash</STRONG> shortly after application startup when <STRONG>OneAgent deep monitoring</STRONG> is enabled.</LI> </UL> <DIV> <UL> <LI><STRONG>Dynatrace OneAgent logs</STRONG> show that assemblies/modules <STRONG>cannot be instrumented</STRONG></LI> <LI>Example logs line from OneAgent logs - <PRE><CODE>Module is unsupported (obfuscated or unsupported version). Skipping instrumentation. (AppConfig.dll)<BR /></CODE></PRE> </LI> </UL> </DIV> <DIV>&nbsp;</DIV> <DIV><STRONG>Why this happens</STRONG></DIV> <DIV> <P><STRONG>ConfuserEx</STRONG><SPAN>&nbsp;is a .NET obfuscation tool that includes&nbsp;</SPAN><STRONG>anti‑debugging and anti‑tampering protections</STRONG><SPAN>.</SPAN></P> <DIV> <P>When ConfuserEx detects:</P> <UL> <LI>a debugger,</LI> <LI>a profiler,</LI> <LI>or runtime instrumentation (such as Dynatrace OneAgent deep monitoring), it intentionally terminates the process by calling: <DIV> <PRE><CODE>Environment.FailFast</CODE></PRE> </DIV> </LI> </UL> <DIV> <P>This behavior is implemented directly in ConfuserEx, as shown here:<SPAN>&nbsp;</SPAN></P> <span class="lia-inline-image-display-wrapper lia-image-align-inline" image-alt="bhaveshbjoshi_1-1769495875418.png" style="width: 15px;"><img src="https://community.dynatrace.com/t5/image/serverpage/image-id/31750i106F82F0DD784C38/image-dimensions/15x15?v=v2" width="15" height="15" role="button" title="bhaveshbjoshi_1-1769495875418.png" alt="bhaveshbjoshi_1-1769495875418.png" /></span><SPAN>ConfuserEx source (AntiDebug.Safe.cs)</SPAN> <P><A href="https://github.com/yck1509/ConfuserEx/blob/v1.0.0/Confuser.Runtime/AntiDebug.Safe.cs#L13" target="_blank" rel="noopener nofollow noreferrer">https://github.com/yck1509/ConfuserEx/blob/v1.0.0/Confuser.Runtime/AntiDebug.Safe.cs#L13</A></P> <DIV><span class="lia-inline-image-display-wrapper lia-image-align-inline" image-alt="bhaveshbjoshi_1-1769495875418.png" style="width: 15px;"><img src="https://community.dynatrace.com/t5/image/serverpage/image-id/31750i106F82F0DD784C38/image-dimensions/15x15?v=v2" width="15" height="15" role="button" title="bhaveshbjoshi_1-1769495875418.png" alt="bhaveshbjoshi_1-1769495875418.png" /></span> Microsoft documentation-&nbsp;<SPAN>Environment.FailFast Method</SPAN></DIV> <DIV> <DIV> <P><A href="https://learn.microsoft.com/en-us/dotnet/api/system.environment.failfast" target="_blank" rel="noopener nofollow noreferrer">https://learn.microsoft.com/en-us/dotnet/api/system.environment.failfast</A></P> </DIV> </DIV> </DIV> </DIV> </DIV> <DIV>It's important to note that Applications using ConfuserEx are known to be incompatible with the Dynatrace OneAgent, and crashes in such scenarios are expected. As a result, using ConfuserEx with the Dynatrace .NET agent is not supported.</DIV> <H2>&nbsp;</H2> <H2>Troubleshooting steps</H2> <UL> <LI>Confirm with the application&nbsp;<SPAN>Developers whether ConfuserEx or any other obfuscator is used.</SPAN>&nbsp;</LI> <LI>Check for OneAgent logs with entry -&nbsp;<CODE>Module is unsupported (obfuscated or unsupported version). Skipping instrumentation. (AppConfig.dll)</CODE></LI> <LI>Check the windows event logs. You may search for following entry in the Windows Events.</LI> </UL> <span class="lia-inline-image-display-wrapper lia-image-align-inline" image-alt="bhaveshbjoshi_2-1769495918732.png" style="width: 400px;"><img src="https://community.dynatrace.com/t5/image/serverpage/image-id/31751iF0F2B3D565804CA4/image-size/medium?v=v2&amp;px=400" role="button" title="bhaveshbjoshi_2-1769495918732.png" alt="bhaveshbjoshi_2-1769495918732.png" /></span> <H2>&nbsp;</H2> <H2>Resolution</H2> <DIV><STRONG>Option 1:</STRONG>&nbsp;Disable deep monitoring for the affected process group.<BR /><STRONG>Option 2:</STRONG>&nbsp;Rebuild the application without ConfuserEx obfuscation.</DIV> <H2>&nbsp;</H2> <H2>Note:</H2> <P>In some scenarios the obfuscation tool may not crash the process but might lead to missing code-level data in trace and break some trace correlation.</P> <H2>What's next</H2> <P>If this article did not help, please open a support ticket, mention that this article was used and provide the following in the ticket:</P> <UL> <LI>OneAgent Support Archive from the affected host.</LI> </UL> </DIV> </DIV> </DIV> Thu, 16 Apr 2026 09:51:04 GMT bhaveshbjoshi 2026-04-16T09:51:04Z IIS Application Pools Crash When OneAgent Deep Monitoring Is Enabled (ConfuserEx Obfuscation) https://community.dynatrace.com/t5/Troubleshooting/IIS-Application-Pools-Crash-When-OneAgent-Deep-Monitoring-Is/ta-p/292795 <P><LI-TOC indent="15" liststyle="disc" maxheadinglevel="2"></LI-TOC></P> <DIV class="lia-message-template-content-zone"> <P>*<EM>Use a table of contents for longer articles.&nbsp;</EM></P> <H1>Summary</H1> <P><EM>*This is a mandatory section.</EM></P> <P><EM>Short description of which part of the Dynatrace platform the article refers to and what kind of problem it will help resolve / task it will describe.</EM></P> <P>&nbsp;</P> <H1>Problem</H1> <P><EM>*This is a mandatory section.</EM></P> <P><EM>Provide a precise description of the problem / task to be described.</EM></P> <P>&nbsp;</P> <H1>Troubleshooting steps</H1> <P><EM>*This section can be omitted.</EM></P> <P>&nbsp;</P> <H1>Resolution</H1> <P><EM>*This section can be omitted for ticket‑creation articles.</EM></P> <H1>What's next</H1> <P><EM>*This is a mandatory section.</EM></P> </DIV> Thu, 16 Apr 2026 09:51:04 GMT https://community.dynatrace.com/t5/Troubleshooting/IIS-Application-Pools-Crash-When-OneAgent-Deep-Monitoring-Is/ta-p/292795 bhaveshbjoshi 2026-04-16T09:51:04Z