Actually all users are "yc", and I didn't add any other user, just root and my user account.
I don't think someone is telnetting into my machine but I disabled telnet anyway (had to do some research to find out how)  
 yc@linux:~> ps -ef | grep yc
yc        2313  2288  0 18:45 ?        00:00:00 /bin/sh /usr/X11R6/bin/kde
yc        2329     1  0 18:45 ?        00:00:00 /opt/gnome/bin/medusa-idled
yc        2367     1  0 18:45 ?        00:00:00 kdeinit: Running...
yc        2370     1  0 18:45 ?        00:00:00 kdeinit: dcopserver --nosid
yc        2373     1  0 18:45 ?        00:00:00 kdeinit: klauncher
yc        2375     1  0 18:45 ?        00:00:01 kdeinit: kded
yc        2381  2367  0 18:45 ?        00:00:00 /opt/kde3//bin/artsd -F 5 -S 409                                                              6 -s 5 -m artsmessage -l 3 -f
yc        2383     1  0 18:45 ?        00:00:00 kdeinit: knotify
yc        2385  2313  0 18:45 ?        00:00:00 kwrapper ksmserver --restore
yc        2387     1  0 18:45 ?        00:00:00 kdeinit: ksmserver --restore
yc        2388  2367  0 18:45 ?        00:00:00 kdeinit: kwin -session 11c0a8010                                                              1000102434161500000111900000
yc        2391     1  0 18:45 ?        00:00:00 kdeinit: kwrited
yc        2393     1  0 18:45 ?        00:00:00 kdeinit: kdesktop
yc        2396     1  0 18:45 ?        00:00:00 kdeinit: kicker
yc        2400     1  0 18:45 ?        00:00:00 kdeinit: klipper -icon klipper -                                                              miniicon klipper
yc        2403     1  0 18:45 ?        00:00:00 kdeinit: kmix -session 11c0a8010                                                              1000102434162000000111900007
yc        2405  2367  0 18:45 ?        00:00:00 kdeinit: konsole -session 11c0a8                                                              0101000102502307700000018640005
yc        2408     1  0 18:45 ?        00:00:00 korgac --miniicon korganizer
yc        2410     1  0 18:45 ?        00:00:00 kalarmd -session 11c0a8010100010                                                              2466635900000018820004
yc        2411  2405  0 18:45 pts/1    00:00:00 /bin/bash
yc        2425  2411  0 18:49 pts/1    00:00:00 ps -ef
Seeing all of this there seems to be a lot of things that belong to KDE and if I run the "w" command I get this 
 6:55pm  up 20 min,  3 users,  load average: 0.01, 0.06, 0.08
USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU  WHAT
yc       :0       console           6:45pm   ?     0.00s   ?     -
yc       pts/0    -                 6:45pm 10:18   0.00s   ?     -
yc       pts/1    -                 6:45pm  0.00s  0.06s  0.01s  w
So I really don't thik there's anything wrong, it just seems odd that it lists 3 users (please someone correct me if I'm wrong) and also I an't remember always having 3 users listed.
At the very least this has served a useful purpose since I found some pretty interesting sites about Linux and security ...