Hey there,
Are you still looking for a solution for this?
Unfortunately, I don’t believe the Filter views can handle search on a M2M relationship, out of the box.
In terms of within-CRM-functionality, while it doesn’t quite meet the same criteria, you could perhaps try creating a Report that lists all Leads by Security Group
You would have the data, at least.
Otherwise, you would have to make code-level changes.
I’m not 100% sure what would be required to achieve this, but I have found the following thread regardinga similar situation.
(But with Contacts<->Projects)
You could try to adapt this code, if you are comfortable making code-level changes?
(Granted, I haven’t tried this myself, so I can’t guarantee it would resolve your issue)