Some of my users are logging in with this browser:
Apache-HttpClient/UNAVAILABLE (java 1.4). What browser is this?
The user agent belongs to Apache HTTPComponents, which is a Java library that handles HTTP request. For example: It could be an Android app that is using the library to send POST requests to your login script. The
UNAVAILABLE part is typically where the version number is located. As far as I know, this user agent is used as the default user agent for requests (i.e. the developer failed to set a custom user agent while setting up their client)
It's from Tor browsers like Orweb and Orfox.