This warning dialog box appears when you attach to a process that contains partially trusted code or is owned by an untrusted user immediately before the attach occurs. An untrusted process that contains malicious code has the potential to damage the computer doing the debugging. If you have reason to distrust the process, then you should click Cancel to prevent debugging.

If you are debugging a legitimate scenario that causes this warning to appear, and want to suppress it, there is a registry setting that allows you to do this. Remember to re-enable the warning after you are done with the scenario.

"Trusted users" include yourself, plus a set of standard users who are typically defined on computers that have the .NET Framework installed, such as aspnet, localsystem, networkservice, and localservice.