Enabling Growth Through Performance
Enabling Growth Through Performance

Nuances of the Microsoft Windows UAC

Nuances of the Microsoft Windows UAC/LUA and its effects on performance monitoring.

The UAC (User Account Controls) and LUA (Limited User Account) have an effect on the way that privileged tools such as VPS implement account impersonation. Lets demystify what can sometimes seems like a daunting problem of access control and escalation.

The confusion starts when an account is unable to be used for impersonation because it has too many rights – or more specifically Administrators rights. The key to successful impersonation is limiting the account on the VPS server to a regular ol’ user account. It can be an administrator of the machine you want it to monitor – but leave it limited on the VPS server!

VPS can monitor many servers and each of them can be monitored using a different windows credential. VPS will run a crawler process as each of these credentials using impersonation. The VPS service will launch a separate process for each distinct credential and use it to funnel the performance metrics to the VPS repository database.

…but here’s the problem: The UAC/LUA really plays no role at the Windows service level. While the services which run there have a lot of permissions they do not SPECIFICALLY have administrators’ rights. This means that if you add a scanner credential to VPS that has administrators’ rights on the VPS server then windows will “detect” that a lower-level permission is attempting to run a process with higher-level permissions. Elevation is not allowed at this level.

It is therefore important that the accounts you use to monitor remote servers NOT be members of the administrator’s group on the VPS server itself. For clarity, the account CAN be an administrator on the server which is being monitored – but not on the server for which the VPS server is installed.

An alternative to the rule which allows for a bit of flexibility

There is actually a small caveat which works to our favor. If the credential that is configured to monitor a server is the same as the account that is running the VPS services, then it will NOT require impersonation. The VPS services will detect this scenario and will simply run the crawler process as itself. In this way, a local administrators account can be used to monitor the local machine and even remote machines.

What this means is that if you specify an account with administrative permissions when installing VPS, that you can then use that credential to monitor any server for which that account has permissions. In this case, that also includes monition the local server for which VPS is installed.

Disabling the UAC?

No! Don’t do that! First and foremost: we have worked very hard to ensure that there are numerous methods to operate VPS across the entire spectrum of security conscious organizations. That being said, we do no recommend disabling the UAC. First of all because that’s not a reasonable security practice, and lastly because it will not solve the problem we are discussing here.

In order to run fully unencumbered, an administrator would need to fully disable the windows LUA which goes against recommendations of security experts and the designers of the operating system. Additionally, it has negative feature related consequences on Windows 10, Windows 2019 server and presumably beyond.

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