Detecting weak password, port scan

A simple password is the greatest risk facing the server, the administrator is obliged to find out the weak passwords, alert users to reset passwords more secure.
Second, crack the code
Jone the Ripper password cracker is an open source tool that can quickly analyze codon string at a known plaintext ciphertext situation.
Tools introduced

2. Extract the tar xf John-1.8.0.tar.gz

3. 安装yum install gcc gcc-c++ -y
4. Into the src directory the compiler: make linux-x86-64
   

5. Go to the directory run execution ./john, analytical / etc / passwd / etc / shadow
can be seen that the root password has been cracked out