Nine points of experience with UNIX security architecture

Unix| Security

Here is a summary of some personal experiences that are believed to be useful for hacked Unix or unix-clonefreebsd,openbsd,netbsd,linux,etc:
First you can track the source path of intruders through the following system commands and configuration files:

1.who------(see who logged in to the system)
2.W--------(see who logged into the system and what it is doing)
3.last-----(Display system once logged in user and TTYs)
4.lastcomm-(Displays the command that the system used to be running)
5.netstat--(You can view the current network status, such as the IP address of the user who telnet to your machine, and some other network states.) )
6. View the router information.
7./var/log/messages View the login status of external users
8. Use finger to view all landing users.
9. View the login history file (. history.rchist,etc) under/home/username in the user's directory. Post note: ' Who ', ' W ', ' Last ', and ' lastcomm ' commands rely on/var/log/pacct,/ Var/log/wtmp,/etc/utmp to report the information to you. Many savvy system administrators will block these log messages for intruders (/VAR/LOG/*,/VAR/LOG/WTMP,ETC) recommend that you install Tcp_wrapper illegally landing all connections to your machine

The system administrator then shuts down all possible backdoor, and must prevent intruders from externally accessing the internal network. If the intruder discovers that the system administrator has found that he has entered the system, he may try to conceal his traces through RM-RF/*.

Third, we need to protect the following system commands and system configuration files to prevent intruders from replacing the right to modify the system.

1./bin/login
2./usr/etc/in.* (for example: IN.TELNETD)
A service awakened by the 3.INETD Super Daemon (listening port, waiting for request, deriving the corresponding server process). (The following server processes are typically started by inetd:
Fingerd (in), FTPD (21),
Rlogind (KLOGIN,EKLOGIN,ETC), rshd,talkd,telnetd (), tftpd. Inetd can also start other internal services,
Services defined in the/etc/inetd.conf.
4. Netstat,ps,ifconfig,su is not allowed for very root users

The system administrator should periodically observe the system changes (e.g. file, system time, etc.)

1. #ls-lac to see the actual modification time of the file.
2. #cmp file1 file2 to compare changes in file size.

We must prevent illegal users from using the SUID (Set-user-id) program to get root privileges.

1. First we need to discover all the SUID programs in the system.