11.5. xterm Logins Show Up Strangely in who, finger.
Answer:
The xterm that comes with XFree86 2.1 and earlier doesn't correctly understand the format that Linux uses for the /var/adm/utmp file, where the system records who is logged in. It therefore doesn't set all the information correctly. The xterms in XFree86 3.1 and later versions fix this problem.