What can cause the SAP user profile sidadm to corrupt ?

Hi, I am investigating the root cause of the corrupt user profile sidadm as an admin of SAP Portal.
Suddenly sidadm can’t logon, checked the memory usage (top command) was occupied by csh processes ran by sidadm, also the .history file kept increasing and chewing up the disk space very quickly.
To solve the issue, I deleted and re-created the user sidadm.
What could cause the corruption to the user profile ?
Thank you & Regards