System weak password detection

JR

A cryptanalysis tool that supports dictionary-style brute force cracking.
Through password analysis of shadow files, you can detect password strength.
Official website: http://www.openwall.com/john/

Install JR tools

Installation method: make clean system type
main program file is john

Detect weak password accounts

Obtain the shadow file of the Linux/Unix server
Execute the john program, and use the shadow file as a parameter

Brute force cracking of password files

Prepare the password dictionary file, the default is password.lst to
execute the john program, combined with -wordlist=dictionary file

Configuration command

cd /opt
tar zxf john-1.8.0.tar.gz            #解压工具包
yum install -y gcc gcc-c++ make        #安装软件编译工具
cd /opt/john-1.8.0/src  #切换到src子目录
make clean linux-x86-64     #进行编译安装
cp /etc/shadow /opt/shadow.txt     #准备待破解的密码文件
cd /opt/john-1.8.0/run
./john /opt/shadow.txt        #执行暴力破解
./john --show /opt/shadow.txt     #查看已破解出的账户列表
使用密码字典文件
> john.pot 		#清空已破解出的账户列表,以便重新分析
./john --wordlist=./password.lst /opt/shadow.txt		#使用指定的字典文件进行破解

Insert picture description here

Because the password is too complicated and it takes a long time to decipher, I won’t post it here.

Network scan

Network scanning-
NMAP NMAP is a powerful port scanning security evaluation tool that supports ping scanning, multi-port detection and other technologies
#Install the NMAP software package
rpm -qa | grep nmap
yum install -y nmap
Insert picture description here

Common options and scan types of nmap command

-p: Specify the port to scan.
-n: Disable reverse DNS resolution (to speed up scanning).
-sS: TCP SYN scan (half-open scan), only SYN packets are sent to the target. If a SYN/ACK response packet is received, the target port is considered to be listening and the connection is immediately disconnected; otherwise, the target port is considered not open.
-sT: TCP connection scanning, this is a complete TCP scanning method (default scanning type), used to establish a TCP connection, if successful, the target port is considered to be listening for services, otherwise the target port is considered not open.
-sF: TCP FIN scan, open ports will ignore such packets, closed ports will respond to RST packets. Many firewalls only simply filter SYN packets and ignore other forms of TCP attack packets. This type of scan can indirectly detect the robustness of the firewall.
-sU: UDP scan, to detect which UDP services the target host provides, the speed of UDP scan will be slower.
-sP: ICMP scan, similar to ping detection, quickly judge whether the target host is alive, and do not perform other scans.
-P0: Skip ping detection. This method considers that all target hosts are alive. When the other party does not respond to ICMP requests, using this method can avoid abandoning scanning due to failure to ping.

netstat -natp 查看正在运行的使用TCP协议的网络状态信息