您可以執行 linuxconf 或 ntsysv 來查看，並應確實了解每個服務的用途．
以 linuxconf 為例：
linuxconf -> control -> Control service activity ，畫面如下：
WEB、DNS(named)、smb(samba)、sendmail 視貴校需要而定，自行開關，除此之外，必要的有：
atd, crond, inet, keytable, network, random, syslog, xfs(若您跑X window的話)
除此之外，除非您真的了解您的需求，否則全部予以關閉．
ftp stream tcp nowait root /usr/sbin/tcpd in.proftpd
telnet stream tcp nowait root /usr/sbin/tcpd in.telnetd
pop-3 stream tcp nowait root /usr/sbin/tcpd ipop3d
關閉的方法就是在每列前面加上 #
以下是 /etc/inetd.conf 的範例檔：
# # inetd.conf This file describes the services that will be available # through the INETD TCP/IP super server. To re-configure # the running INETD process, edit this file, then send the # INETD process a SIGHUP signal. # # Version: @(#)/etc/inetd.conf 3.10 05/27/93 # # Authors: Original taken from BSD UNIX 4.3/TAHOE. # Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org> # # Modified for Debian Linux by Ian A. Murdock <imurdock@shell.portal.com> # # Modified for RHS Linux by Marc Ewing <marc@redhat.com> # # <service_name> <sock_type> <proto> <flags> <user> <server_path> <args> # # Echo, discard, daytime, and chargen are used primarily for testing. # # To re-read this file after changes, just do a 'killall -HUP inetd' # #echo stream tcp nowait root internal #echo dgram udp wait root internal #discard stream tcp nowait root internal #discard dgram udp wait root internal #daytime stream tcp nowait root internal #daytime dgram udp wait root internal #chargen stream tcp nowait root internal #chargen dgram udp wait root internal #time stream tcp nowait root internal #time dgram udp wait root internal # # These are standard services. # ftp stream tcp nowait root /usr/sbin/tcpd in.proftpd telnet stream tcp nowait root /usr/sbin/tcpd in.telnetd # # Shell, login, exec, comsat and talk are BSD protocols. # #shell stream tcp nowait root /usr/sbin/tcpd in.rshd #login stream tcp nowait root /usr/sbin/tcpd in.rlogind #exec stream tcp nowait root /usr/sbin/tcpd in.rexecd #comsat dgram udp wait root /usr/sbin/tcpd in.comsat #talk dgram udp wait nobody.tty /usr/sbin/tcpd in.talkd #ntalk dgram udp wait nobody.tty /usr/sbin/tcpd in.ntalkd #dtalk stream tcp wait nobody.tty /usr/sbin/tcpd in.dtalkd # # Pop and imap mail services et al # #pop-2 stream tcp nowait root /usr/sbin/tcpd ipop2d pop-3 stream tcp nowait root /usr/sbin/tcpd ipop3d #imap stream tcp nowait root /usr/sbin/tcpd imapd # # The Internet UUCP service. # #uucp stream tcp nowait uucp /usr/sbin/tcpd /usr/lib/uucp/uucico -l # # Tftp service is provided primarily for booting. Most sites # run this only on machines acting as "boot servers." Do not uncomment # this unless you *need* it. # #tftp dgram udp wait root /usr/sbin/tcpd in.tftpd #bootps dgram udp wait root /usr/sbin/tcpd bootpd # # Finger, systat and netstat give out user information which may be # valuable to potential "system crackers." Many sites choose to disable # some or all of these services to improve security. # #finger stream tcp nowait nobody /usr/sbin/tcpd in.fingerd #cfinger stream tcp nowait root /usr/sbin/tcpd in.cfingerd #systat stream tcp nowait guest /usr/sbin/tcpd /bin/ps -auwwx #netstat stream tcp nowait guest /usr/sbin/tcpd /bin/netstat -f inet # # Authentication # #auth stream tcp wait root /usr/sbin/in.identd in.identd -e -o # # End of inetd.conf #linuxconf stream tcp wait root /bin/linuxconf linuxconf --http #swat stream tcp nowait.400 root /usr/sbin/swat swat
或者， /etc/inetd.conf 只存以下三個設定列(其它都刪掉)，亦可．
ftp stream tcp nowait root /usr/sbin/tcpd in.proftpd telnet stream tcp nowait root /usr/sbin/tcpd in.telnetd pop-3 stream tcp nowait root /usr/sbin/tcpd ipop3d之後，記得要重新啟動 inetd ：
/etc/rc.d/init.d/inet restart
a. 先檢查是否有裝 tcp_wrappers ？
rpm -q tcp_wrappers
若出現 tcp_wrappers-7.x-x 即表示 tcp_wrappers 已安裝，若無，請安裝 tcp_wrappers-7.x-x.i386.rpm
b. 通常限制 telnet 及 ftp 的連線範圍
必須設定 /etc/hosts.allow 及 /etc/hosts.deny 這二個檔案，前者，用來設定：哪些服務開放給特定的連線範圍；後者，用來設定：哪些服務拒絕特定連線範圍，優先權是：只要在 hosts.allow 中設定開放的，hosts.deny 中便不會拒絕(即first match first terminates的規則)．
例：
編輯：/etc/hosts.allow
in.telnetd: 163.26.199.0/255.255.255.0, 163.26.198.1, .sample.edu.tw : Allow
in.proftpd: 163.26.199.0/255.255.255.0, 163.26.198.1, .sample.edu.tw : Allow
編輯：/etc/hosts.deny
in.telnetd: ALL : Deny
in.proftpd: ALL : Deny
上面這些設定是說：允許 163.26.199.0 這個 C class 範圍(IP 範圍的例子)，和 163.26.198.1 這部主機(單一IP的例子),以及 sample.edu.tw 這個網域(以網域名稱做判別的例子)的使用者 telnet 及 ftp 連線到我們的主機，而其它連線範圍，則全部拒絕．
請貴校自行調整上面的設定吧！(通常 telnet 設成只限校內及欲由校外連入維護時之IP)
以麻豆國中為例
vi /etc/hosts.allow
in.telnetd: 163.26.197.0/255.255.255.0 : Allow
in.proftpd: 163.26.197.0/255.255.255.0 : Allow
vi /etc/hosts.deny
in.telnetd: ALL : Deny
in.proftpd: ALL : Deny
a. 安裝 nmap (可至 ftp://ftp.tnc.edu.tw/pub/Sysop/nmap 下載)
rpm -ivh nmap-2.3BETA10-2.i386.rpm
或
rpm -ivh nmap*.rpm
b. 掃瞄貴校的主機
nmap 163.26.197.1 (以麻豆國中為例)
像這樣子，該開放的開放，不該開放的全部關閉，便較安全．
*注意：nmap可不能隨便拿來掃射別人的主機喔！(有如小孩拿大槍上街?) 未經站主的允許便掃瞄別人的服務通道，會被視為入侵的一種意圖或行為，往往會引起抗議和法律糾紛喔！不可不小心哪！ (當然有不讓對方知道的方法 ;-) )
*nmap 原始站台：http://www.insecure.org/nmap/