PermitRootLogin no 가 root 로그인 막는게 맞을텐데요. no 인데도 root 로 로그인 되던 비슷한 경험이 한번 있어서 한번 남겨봅니다. 무엇때문인지는 기억 안납니다.

예전에 한번 가이드 작성해둔것과 현재 쓰고 있는 sshd_config 파일 내용입니다.
성공하세요!
http://www.suse.or.kr/bbs/board.php?bo_table=tip&wr_id=2173

#       $OpenBSD: sshd_config,v 1.74 2006/07/19 13:07:10 dtucker Exp $

# This is the sshd server system-wide configuration file.  See
# sshd_config(5) for more information.

# This sshd was compiled with PATH=/usr/bin:/bin:/usr/sbin:/sbin

# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented.  Uncommented options change a
# default value.

#Port 22
Protocol 2
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::

# HostKey for protocol version 1
#HostKey /etc/ssh/ssh_host_key
# HostKeys for protocol version 2
#HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_dsa_key

# Lifetime and size of ephemeral version 1 server key
#KeyRegenerationInterval 1h
#ServerKeyBits 768

# Logging
# obsoletes QuietMode and FascistLogging
#SyslogFacility AUTH
#LogLevel INFO

# Authentication:

#LoginGraceTime 2m
#PermitRootLogin yes
#StrictModes yes
#MaxAuthTries 6

#RSAAuthentication yes
PubkeyAuthentication yes
#AuthorizedKeysFile     .ssh/authorized_keys

# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#RhostsRSAAuthentication no
# similar for protocol version 2
#HostbasedAuthentication no
# Change to yes if you don't trust ~/.ssh/known_hosts for
# RhostsRSAAuthentication and HostbasedAuthentication
#IgnoreUserKnownHosts no
# Don't read the user's ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes

# To disable tunneled clear text passwords, change to no here!
PasswordAuthentication no
#PermitEmptyPasswords no

# Change to no to disable s/key passwords
ChallengeResponseAuthentication no

# Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
#KerberosGetAFSToken no

# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes

# Set this to 'yes' to enable support for the deprecated 'gssapi' authentication
# mechanism to OpenSSH 3.8p1. The newer 'gssapi-with-mic' mechanism is included
# in this release. The use of 'gssapi' is deprecated due to the presence of
# potential man-in-the-middle attacks, which 'gssapi-with-mic' is not susceptible to.
#GSSAPIEnableMITMAttack no


# Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication.  Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
UsePAM yes

#AllowTcpForwarding yes
#GatewayPorts no
X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes
#PrintMotd yes
#PrintLastLog yes
#TCPKeepAlive yes
#UseLogin no
#UsePrivilegeSeparation yes
#PermitUserEnvironment no
#Compression delayed
#ClientAliveInterval 0
#ClientAliveCountMax 3
#UseDNS yes
#PidFile /var/run/sshd.pid
#MaxStartups 10
#PermitTunnel no

# no default banner path
#Banner /some/path

# override default of no subsystems
Subsystem sftp  /usr/lib/ssh/sftp-server

# This enables accepting locale enviroment variables LC_* LANG, see sshd_config(5).
AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv LC_IDENTIFICATION LC_ALL
AllowTcpForwarding yes
Compression yes
MaxAuthTries 6
PermitRootLogin no
PrintMotd yes
RSAAuthentication no

# Example of overriding settings on a per-user basis
#Match User anoncvs
#       X11Forwarding no
#       AllowTcpForwarding no
#       ForceCommand cvs server

ㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡ
RME 9636/52, RomIO, ESP 1010, Triton pro, K2600x, JV-80, Yamaha O3D, Tascam DA-30MKII... etc

ssh_config가 아니라 sshd_config파일을 수정해야 한다는 점에도 주의하시길.

===== ===== ===== ===== =====
그럼 이만 총총...[竹]
http://elflord.egloos.com

PermitRootLogin no

저도 ssh_config에서 설정했다가 피봣습니다 sshd_config 입니다1!
d에 주의하세요..