One of the comments I receive most frequently from attendees of my Least Privilege webinar is that web conferencing software, such as Citrix’s popular GoToMeeting, prevents IT departments moving forward with least privilege on the desktop. This kind of software can pose a problem as users are often requested to join meetings at short notice and need to install a client program to participate in the conference. In this post I’ll focus on GoToMeeting, but some of the information could also be applied to other software.
Citrix has engineered GoToMeeting so that it doesn’t require any special privileges to install. That may come as a surprise to some system administrators, as it’s often assumed that admin rights are required to install and update the software. One exception is that administrative privileges are needed to install GoToMeeting’s recording codec, but if you don’t need to record a meeting, you’re good to go without it.
If you’ve configured application allow listing to provide an extra layer of defense, you’ll need to make the necessary exceptions so users can install and update GoToMeeting. Creating rules for Windows 7 AppLocker to allow GoToMeeting to run needs a little preparation because of the slightly convoluted nature in which GoToMeeting installs and runs.
Rules will be required for 5 executables as shown in Table 1. Assuming you’ve already enabled AppLocker in Windows 7, I won’t explain here how to create rules, as no doubt that’s something you already know how to do. A good primer can be found at http://technet.microsoft.com/en-us/windows/dd320283. Suffice to say that following best practice, you should configure publisher rules for the GoToMeeting runtimes wherever possible. Figure 1 shows how the file name on disk and the file name displayed in the AppLocker wizard differ, adding some confusion to the process.
For the purposes of adding the GoToMeeting runtimes to AppLocker, you’ll find most of the executables located in the logged in user’s TEMP directory (%username%\appdata\local\temp). You can either enable AppLocker and add a rule for each executable as it’s blocked or install GoToMeeting with AppLocker disabled and then run the Automatically Generate Rules wizard and allow AppLocker to discover the necessary runtimes. The appcore executable isn’t signed, so you’ll need to create a file hash or path file rule to prevent AppLocker from blocking it.
Once rules to allow the 5 executables listed in Table 1 are added to AppLocker, you should find that users can join and host meetings. If you’re using a mix of Windows versions, Privilege Guard can manage application privileges and implement allow listing in XP and later so that one set of rules are applied to all your Windows systems.
Use Virtualization to Solve Problems of Privilege
If a user is required to host meetings on a regular basis, with GoToMeeting or a different service, make sure the software is set up in advance and works on their local desktop. For users that might need to join meetings at short notice using unknown services, consider deploying Windows 7 XP Mode - or other virtualized desktop - so that if necessary, client software can be quickly installed without any intervention from IT.