Remko Weijnen's Blog (Remko's Blog)

About Terminal Server, Citrix, Delphi and other stuff

Session freeze when starting Excel

Environment
Windows 2003 Enterprise (32 bit), Citrix XenApp 5, RES Workspace Manager 2011, McAfee VirusScan Enterprise 8.7.0i.

Problem
When a opening an Excel workbook from Sharepoint the whole session freezes.

I asked the user to open an Excel workbook from Sharepoint and I noticed the following popup:

Some files can harm your computer. If the file information looks suspicious or you do not fully trust the source, do not open the file | You are opening the following file: | File name: My Workbook.xls | From: Sharepoint

So my first thought was that the user somehow clicked this message to the background and IE was waiting for a response.

(more…)

The XLSploit explained

Recently I published a Proof of Concept that showed it was possible to launch unauthorized processes with both AppSense Application Manager and RES Workspace Manager.

Although I didn’t test Microsoft Applocker I have no doubt at all that we couldn’t bypass it.

imageI have named my Proof of Concept the XLSploit because I am using Excel as a trampoline. I choose Excel because this is generally a trusted process and VBA offers access to the Windows API that is needed.

After publishing the XLSploit I have talked to both RES and AppSense and not that they both have a response to my Proof of Concept, I consider it safe to tell a little more about how it works.

If you are merely interested in stopping the XLSploit, please scroll down to the end of the article.

(more…)

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