Real Case: .Net Apps – "No connection could be made because the target machine actively refused it" (basic)

Recently we’ve been receiving (by coincidence) some escalations to troubleshoot the same issue.  It’s about .Net apps returning the following exception:   SocketException::.ctor() 10061:No connection could be made because the target machine actively refused it   The cases I’ve been working with show different stack traces but the main point here is that exception is…

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Real Case: IIS and Asp.Net hanging or poor performance (intermediary)

This week I’m working on this case related to IIS6 server hosting an Asp.Net application (it’s a C# app) whose the performance is poor even when a very low number of users is hitting it.  The architecture is the classical web layer accessing the backend DB servers and my goal is to isolate the problem, i.e pinpoint where…

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A Virus Infection: Contolling the Outbreak (tip)

This weekend I had the opportunity to work along our security specialists (from PSSSec group) in what we can call the hottest situation involving hundreds of production servers either stopped or severely impacted by a new variation of a worm.   As a new variation, the AV signature file wasn’t updated with the proper signature and once the…

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Lab: Win32 Application causing 100% CPU condition (Advanced)

This is lab for simulating a real 100% CPU condition being caused by a generic Win32 application when there are no symbols available for such application.     Let’s start supposing the situation is currently occurring.  So, the first step is to confirm the symptoms, which we can easily do by using, for instance the…

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Troubleshooting IIS 100% CPU issues – Step by Step (intermediary)

Processes consuming 100% of a system’s CPU time is such a situation everybody has faced at least once (likely much more than once :)), and normally as solution we just “kill the murderer” by stopping the culprit process.  But what was really causing that process to behave like that?  If you can’t properly answer this question you might…

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/3GB, /PAE, AWE what??? (basic)

I’ve been following the discussions about these options for a long time. When it seems that everybody agrees on something, somebody else comes with a different understanding and the discussion starts all over again… The questions at the beginning of each thread about this subject are often the same: When should I use /3GB option,…

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Perfmon’s counters output format (tip)

The System Monitor (Perfmon.exe) reports the data gathered through some of its objects and counters with no formatting and depending on what kind of counters are you looking at, or how tired you are, sometimes this can be confusing and even cause misinterpretation problems. As an example, take the counter Processes::Virtual Bytes.  We normally have MBytes or…

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