Verify the telnet plaintext transmission password for wireshark packet capture in CentOS

Host-

IP: 192.168.56.129OS: RHEL5.932bitService: telnet-server

Host-B

IP: 192.168.56.128OS: RHEL5.932bitService: telnet-client

View Nic information on HostA

12345678910 #ifconfigeht0 eth0Linkencap:EthernetHWaddr 00 :0C: 29 :CC: 30 :9A inetaddr: 192.168 . 56.129 Bcast: 192.168 . 56.255 Mask: 255.255 . 255.0 inet6addr:fe80::20c:29ff:fecc:309a/ 64 Scope:Link UPBROADCASTRUNNINGMULTICASTMTU: 1500 Metric: 1 RXpackets: 4914 errors: 0 dropped: 0 overruns: 0 frame: 0 TXpackets: 3705 errors: 0 dropped: 0 overruns: 0 carrier: 0 collisions: 0 txqueuelen: 1000 RXbytes: 2419811 ( 2.3 MiB)TXbytes: 276508 ( 270.0 KiB) Interrupt: 67 Baseaddress: 0x2024

Start the telnet Service

Install wireshark packet capture tool

12 #yuminstall-ywireshark #yuminstall-ywireshark-gnome // Install the command line tool and the gnome graphical tool package together

Enable wireshark packet capture. To facilitate packet analysis, the Filtering Rule tcp. port = 23andip. dst = 192.168.56.129 is written.

Log on to 192.168.56.129 via telnet as the root user on the host 192.168.56.128. First, view the NIC information.

12345678910 #ifconfigeth0 eth0Linkencap:EthernetHWaddr 00 :0C: 29 :E8:F9:FE inetaddr: 192.168 . 56.128 Bcast: 192.168 . 56.255 Mask: 255.255 . 255.0 inet6addr:fe80::20c:29ff:fee8:f9fe/ 64 Scope:Link UPBROADCASTRUNNINGMULTICASTMTU: 1500 Metric: 1 RXpackets: 3518 errors: 0 dropped: 0 overruns: 0 frame: 0 TXpackets: 4232 errors: 0 dropped: 0 overruns: 0 carrier: 0 collisions: 0 txqueuelen: 1000 RXbytes: 276736 ( 270.2 KiB)TXbytes: 2356751 ( 2.2 MiB) Interrupt: 67 Baseaddress: 0x2024

Use the root user logon password as redhat. The logon is successful!

Capture packets with wireshark at 192.168.56.129

We can clearly see that the username is "root" and the password is "redhat". Therefore, telnet is a plaintext transmission protocol that is extremely insecure. We recommend sshv2.

The above operation proves the plaintext transmission password of telnet, and the Protocol does not undergo any encryption measures, so we hope to have a deep understanding. In addition, there are also plain text transmission passwords like ftp, rlogin, smtp, and pop3, but the most dangerous thing is telnet, because the user name and password of the operating system are the ones that are hijacked.