localize o phpMyAdmin.conf em um dos diretórios httpd config e adicione deny 73.199.136.112
na seção allow / deny do arquivo de configuração e solicite um IP na seção 2.4. Eu coloquei um exemplo do arquivo de configuração completo abaixo, onde eu tenho as entradas em ordem inversa, eu bloqueio tudo, mas os segmentos IP permitidos para acessar a ferramenta.
[thebtm@server conf.d]# cat /etc/httpd/conf.d/phpMyAdmin.conf
# phpMyAdmin - Web based MySQL browser written in php
#
# Allows only localhost by default
#
# But allowing phpMyAdmin to anyone other than localhost should be considered
# dangerous unless properly secured by SSL
Alias /phpMyAdmin /usr/share/phpMyAdmin
Alias /phpmyadmin /usr/share/phpMyAdmin
<Directory /usr/share/phpMyAdmin/>
AddDefaultCharset UTF-8
<IfModule mod_authz_core.c>
# Apache 2.4
<RequireAny>
Require ip 10.10.26
Require ip 192.168.56
Require ip 127.0.0.1
Require ip ::1
</RequireAny>
</IfModule>
<IfModule !mod_authz_core.c>
# Apache 2.2
Order Deny,Allow
Deny from All
Allow from 10.10.25
Allow from 192.168.56
Allow from 127.0.0.1
Allow from ::1
</IfModule>
</Directory>
<Directory /usr/share/phpMyAdmin/setup/>
<IfModule mod_authz_core.c>
# Apache 2.4
<RequireAny>
Require ip 127.0.0.1
Require ip ::1
</RequireAny>
</IfModule>
<IfModule !mod_authz_core.c>
# Apache 2.2
Order Deny,Allow
Deny from All
Allow from 127.0.0.1
Allow from ::1
</IfModule>
</Directory>
# These directories do not require access over HTTP - taken from the original
# phpMyAdmin upstream tarball
#
<Directory /usr/share/phpMyAdmin/libraries/>
Order Deny,Allow
Deny from All
Allow from None
</Directory>
<Directory /usr/share/phpMyAdmin/setup/lib/>
Order Deny,Allow
Deny from All
Allow from None
</Directory>
<Directory /usr/share/phpMyAdmin/setup/frames/>
Order Deny,Allow
Deny from All
Allow from None
</Directory>
# This configuration prevents mod_security at phpMyAdmin directories from
# filtering SQL etc. This may break your mod_security implementation.
#
#<IfModule mod_security.c>
# <Directory /usr/share/phpMyAdmin/>
# SecRuleInheritance Off
# </Directory>
#</IfModule>