Typically, those types of applications don’t require elevation unless they are attempted to perform a restricted action that would prompt the UAC window.

One way to do this would be leveraging Drive criteria. This would at least cover your removable media.

By the definition of portable app, it’s also called a standalone software - which means it is designed to operate without changing other files. Elevation activity is most likely rare.

Creating a rule based on Drive type will only target the ones running on non-Fixed disk, but it will not be able to cover the ones copied to Fixed Disk to execute.

The only method I can think of, that can fully address this is a full fledged Allow List - where only approved software can run - all others will be halted/blocked.

When applying a block, try to avoid multiple criteria as it makes the block easier to defeat. All criteria must be met for it to be blocked, so renaming, running from a deferent location or re-signing could be used by a user who understands how the block is applied.

Sounds like you want to block any unknown .exes. This is default behaviour for the Quick Start Low Flexibility workstyle as files copied to an external drive or those copied to the endpoint will be owned (NTFS ownership) by the user and therefore fall into through to the “(Default) Any Application” rule:

The user will be shown a message that requires external authorization.

If the user has the High Flexibility workstyle, then these untrusted applications will be allowed to run as the “(Default) Any Application” is applied differently in here:

Note there is no message set, so the process is allowed to run.

How does the untrusted app end up in the “(Default) Any Application” rule?

It is simply because no other rule above matched it.

Trusted exes are matched in “Passive - Allowed Functions & Apps”

It is because of this criterion:
 

Note that “Any Trusted Executable” includes other criterion:

Does not match: (powershell_ise.exe)|(powershell.exe)|(cmd.exe)|(wscript.exe)|(cscript.exe)|(mshta.exe)

Drive: is Fixed Disk

Trusted Ownership: is a Trusted Owner

So even files on an external drive that are trusted should not match the rule and drop through to “(Default) Any Application”.

Back to the original question of how to block portable apps. All exes are the same essentially, regardless of how they were deployed and EPM can’t differentiate between an exe that was deployed by an installer or a self contained one. It can stop the execution of exes from untrusted sources which should cover your use-case. 

You can, of course, add exceptions by adding the exe to “Passive - Allowed Functions & Apps”. Here, unlike for blocking, it is a good idea to use multiple criteria in order to make it harder to allow execution. E.g. Filename + Product name.

Thank you for the insights.

A little background story, most users in my client environment treat the company computers like personal ones. They do download games, music, videos, torrents, editing photos, etc, while working.

Since new software installation is blocked, they always find ways to do what they want, like downloading with some sort of portable torrent clients, portable download managers, portable 7zip, portable photoshop, etc, as these applications don't need to be installed.

So, I'm trying to limit what can be run, including portable apps.

I think I will recommend my client to use low flexibility workstyle combined with a whitelist approach. Because ideally, the number of allowed applications should be far fewer than the unknown ones, regardless of whether they are portable apps or any other executable.