Strange error in ASP.NET

Question

Every once in a while I get about 10 - 20 identical errors on my asp.net app. It's always the same, and I'm wondering if it is someone trying to hack in (it happens about once a month).

Source: System.Web

Message: The file '/~/Default.aspx' does not exist.

User IP: 89.122.29.80

User Browser: Unknown 0.0

User OS: Unknown

Stack trace: at System.Web.UI.Util.CheckVirtualFileExists(VirtualPath virtualPath) at System.Web.Compilation.BuildManager.GetVPathBuildResultInternal(VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile) at System.Web.Compilation.BuildManager.GetVPathBuildResultWithNoAssert(HttpContext context, VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile) at System.Web.Compilation.BuildManager.GetVirtualPathObjectFactory(VirtualPath virtualPath, HttpContext context, Boolean allowCrossApp, Boolean noAssert) at System.Web.Compilation.BuildManager.CreateInstanceFromVirtualPath(VirtualPath virtualPath, Type requiredBaseType, HttpContext context, Boolean allowCrossApp, Boolean noAssert) at System.Web.UI.PageHandlerFactory.GetHandlerHelper(HttpContext context, String requestType, VirtualPath virtualPath, String physicalPath) at System.Web.UI.PageHandlerFactory.System.Web.IHttpHandlerFactory2.GetHandler(HttpContext context, String requestType, VirtualPath virtualPath, String physicalPath) at System.Web.HttpApplication.MapHttpHandler(HttpContext context, String requestType, VirtualPath path, String pathTranslated, Boolean useAppConfig) at System.Web.HttpApplication.MapHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean completedSynchronously)

why on earth would someone be trying to access "/~/Default.aspx" ?

Answer 1

Maybe it is because of the robot or the crawler.

Answer 2

On any well trafficked web site you'll get numerous 404 errors from badly written crawlers, badly written caching servers anti-virus software and browser toolbar add-ons as they each try to second guess what URLs lead off a page. Often they will misinterpret embedded Javascript trying to figure out what pages it might be linking to.

BUT I've never seen one with a ~ character in it. That implies you had a ~ on a page which implies that you have a literal ~/Default.aspx occurring somewhere on a page. Can you find the page in question and do view source on it to see if there's a ~ somewhere on it?

If you vary the page contents according to user agent, can you replay the same request and look at the source?

Have you run a link checker against you site?

Answer 3

This sometimes happens if you are trying to set the NavigateUrl on a HyperLink control too late in the page lifecycle. Make sure that you are not creating HyperLinks in your code behind after the relative Urls are generated.