第一種方法： 屏蔽telnet功能。 telnet功能被屏蔽掉後，任何用戶都無法登錄，當然ROOT也無法登錄。但這種方法太過極端。故不可取。
第二方法： 在/etc/default/login中增加一行命令 CONSOLE＝tty01 經過這樣設置後，用戶只能在第一個控制台上以ROOT登錄。任何其他控制台和所有遠程用戶均無法登錄。
第三種方法： 只允許指定的用戶以ROOT用戶遠程登錄 若服務器的地址為134.33.86.13;允許地址為134.33.86.17和134.33.86.18的機器以ROOT登錄。 1. 首先編輯/etc/hosts文件，內容如下： 127.0.0.1 local 134.33.86.13 jnzy.jndx.com 134.33.86.17 root2 134.33.86.18 root3 2. 寫一段程序放入文件/.profile中 # @(#) root.profile 68.1 98/01/20 # # Copyright (C) 1989-1998 The Santa Cruz Operation, Inc. # All Rights Reserved. # The information in this file is provided for the exclusive use of # the licensees of The Santa Cruz Operation, Inc. SUCh users have the # right to use, modify, and incorporate this code into other products # for purposes authorized by the license agreement provided they include # this notice and the associated copyright notice with any such product. # The information in this file is provided "AS IS" without warranty. # TY=`ttycut -b 9-12` WH=`fingercut -b 32-79grep "$TY"cut -b 29-39` KK=`ttycut -b 6-9` if [ "$KK" = "ttyp" ] then WH=$WH else WH="local" fi trap 1 2 3 9 15 if [ "$WH" = "local" -o "$WH" = "root2" ] then SHELL=/bin/sh HOME=/ PATH=/bin:/etc:/usr/bin:/tcb/bin:/zy # set terminal type eval `tset -m scoansi:${TERM:-scoansi} -m :\?${TERM:-scoansi} -e -r -s -Q` eXPort TERM PATH SHELL HOME [ -x /bin/mesg ] && mesg n # if mesg is installed... date else echo "you can not telnet by root：\07\07" #拒絕登錄並響鈴告警 echo "press any key to exit"＃按任意鍵退出 read sad exit fi 這樣只有在IP地址為134.33.8.17和134.33.86.18兩台機器上能以ROOT用戶登錄，其他地址不可以用ROOT登錄。 從而保證系統安全。
