Block Telnet in ASA Firewall

[abhisheksingh757821668]

Hi Team,

We want to know about block telnet on ASA firewall. If just like RDP service is working on 3389 TCP port. So we want to user not able to telnet 3389 port but actually service is working on same port 3389. So after this process no one is doesn't known about listening ports.

Example is : Always showing in attachment.

Regards,

Abhishek

[ngkin2010 · Accepted solution]

Hi,

The telnet command only establish TCP 3-way handshake (which mean no application data), none of the firewall (even it has the ability of application awareness) could identify if the traffic is a normal application traffic or it's established through telnet client.

So there is not possible to block it on network layer.

If there is some suspicious actions like port scanning (not a single port, but scanning multiple ports in a short period of time), you could adopt IPS / ATP to detect the suspicious traffic pattern and eventually stop the traffic.