Is there any simple way to lock stream temporarily?
Accepted answer
The easiest way to temporarily modify permissions on a stream is to change the owner to a project/team area that has a very limited membership. The action can be performed with the commandline or rich UIs, and is very quick. It has the benefit of assigning a consistent set of behaviours to the stream, so that it can remain read-only, or modifiable by some subset of users.
There are alternatives, but they depend on your use case. Can you tell us a bit more about what you're trying to do?
If you want to lock streams regularly (during the endgame of a release, for example), you may want to consider assigning behaviour or permissions to iteration types.