SSH hangs after authentication

There are several things that can cause a hang right after SSH authentication.

However most of these will also carry other symptoms (the hang right after an SSH-auth is just the most visible symptom)

1. As Iain mentioned, any user login scripts.
   • ~/.bashrc, ~/.bash_profile, ~/.profile, ~/.kshrc and so forth
2. Too many processes running / restarting.
   • Something has fork()‘d too many child-processes and the load (the 1/5/15 score) is too high.
3. There is an I/O wait problem.
   • Typically caused by a dying hard-drive (common) or a badly behaving NIC (rare).
4. A 3rd-Party PAM module hanging (eg: a non-standard Kerberos config)
   • Not always the module itself, but sometimes a service (like auditing) that has a full log-server somewhere.