09-14-2010 10:21 PM - edited 03-10-2019 05:24 PM
Hi,
I was wondering whether there was a way to dynamically block a vty session (telnet/ssh etc) for a period of time after x amount of failed login attempts using Cisco IOS? I don't believe there is, but I wanted a way to provide Internet connectivity to a router but stop DDoS attempts from filling up the available VTY lines and/or bots continually trying to log in.
Thanks,
goulin
Solved! Go to Solution.
10-12-2010 07:13 AM
Here it is:
http://www.cisco.com/en/US/docs/ios/sec_user_services/configuration/guide/sec_login_enhance.html
You can even exept certain IPs from being blocked.
A sample:
login block-for 60 attempts 5 within 30
!this will block anyone for 60s when 5 unsuccessful logins occurs within 30s
10-11-2010 11:02 AM
I did a little testing and do not see a way to do this, sorry
10-12-2010 07:13 AM
Here it is:
http://www.cisco.com/en/US/docs/ios/sec_user_services/configuration/guide/sec_login_enhance.html
You can even exept certain IPs from being blocked.
A sample:
login block-for 60 attempts 5 within 30
!this will block anyone for 60s when 5 unsuccessful logins occurs within 30s
10-12-2010 05:20 PM
Hi Bastien,
Thanks for that. It is pretty close to what I am after... certainly better than leave it open (I can use the ACL to allow only known addresses during a DDoS event).
Regards,
goulin
07-22-2019 01:20 PM - edited 07-22-2019 01:31 PM
A routing device can be configured to react to repeated unsuccessful logon attempts by rejecting an additional connection request (logon lock). This block can be configured for a period of time, called 'period of silence'. Legitimate connection attempts can still be allowed during a period of silence by configuring an access list (ACL) with addresses that you know are associated with system administrators.
Configuration of the login parameters
- block login attempts for second attempts in seconds
- login in silent mode access class {acl-name | acl-number}
- seconds of delay of login
Example:
Parameters that help provide DoS detection
Router(config)#login block for 100 attempts 2 within 100
Router(config)#login quiet-mode access-class myacl
Router(config)#login delay 10
(Optional) Set a delay between successive logon attempts.
For more details:
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