Linux网络安全技巧

echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all

telnet stream tcp nowait root /usr/sbin/tcpd in.telnetd -h

# Lookup names via DNS first then fall back to /etc/hosts.
order bind,hosts
# We don have machines with multiple IP addresses on the same card
(like virtual server,IP Aliasing).
multi off
# Check for IP address spoofing.
nospoof on
IP Spoofing: IP-Spoofing is a security exploit that works by tricking
computers in a trust relationship that you are someone that you really aren .

tty1
#tty2
#tty3
#tty4
#tty5
#tty6
#tty7
#tty8

[root@deep]# userdel username

[root@deep]# groupdel username

[root@deep]# userdel adm
[root@deep]# userdel lp
[root@deep]# userdel sync
[root@deep]# userdel shutdown
[root@deep]# userdel halt
[root@deep]# userdel mail

[root@deep]# userdel news
[root@deep]# userdel uucp
[root@deep]# userdel operator
[root@deep]# userdel games

[root@deep]# userdel gopher
[root@deep]# userdel ftp

打入下面的命令删除组帐号
[root@deep]# groupdel adm
[root@deep]# groupdel lp
[root@deep]# groupdel mail
如不用Sendmail服务器，删除这个组帐号
[root@deep]# groupdel news
[root@deep]# groupdel uucp
[root@deep]# groupdel games
如你不用X Windows，删除这个组帐号
[root@deep]# groupdel dip
[root@deep]# groupdel pppusers
[root@deep]# groupdel popusers
如果你不用POP服务器，删除这个组帐号
[root@deep]# groupdel slipusers

用下面的命令加需要的用户帐号
[root@deep]# useradd username
用下面的命令改变用户口令
[root@deep]# passwd username
用chattr命令给下面的文件加上不可更改属性。
[root@deep]# chattr +i /etc/passwd
[root@deep]# chattr +i /etc/shadow
[root@deep]# chattr +i /etc/group
[root@deep]# chattr +i /etc/gshadow

auth sufficient /lib/security/pam_rootok.so debug
auth required /lib/security/pam_wheel.so group=isd

[root@deep]# usermod -G10 admin