第三步:编辑“inetd.conf”文件(vi /etc/inetd.conf),禁止所有不需要的服务,如:ftp、 telnet、 shell、 login、 exec、talk、ntalk、 imap、 pop-2、pop-3、finger、auth,等等。
如果你觉得某些服务有用,可以不禁止这些服务。但是,把这些服务禁止掉,系统受攻击的可能性就会小很多。改变后的“inetd.conf”文件的内容如下面所示:
# 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.ftpd -l -a #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 root /usr/sbin/tcpd in.talkd #ntalk dgram udp wait root /usr/sbin/tcpd in.ntalkd #dtalk stream tcp wait nobody /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 root /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 nowait nobody/usr/sbin/in.identd in.identd -l -e -o # # End of inetd.conf |
注意:改变了“inetd.conf”文件之后,别忘了给inetd进程发一个SIGHUP信号(killall –HUP inetd)。