Too many security failures


What causes this message?

VNC Server has a 'blacklisting' scheme that blocks an IP address after five unsuccessful connection attempts. This is a security feature to prevent against DOS and Brute Force attacks against your Computer.

The IP address is initially blocked for 10 seconds, but this doubles for each unsuccessful attempt thereafter.

A successful connection from an IP address resets the blacklist timeout. This is built in to VNC Server and does not rely on operating system support.

How do I reset the timeout?

To reset the blacklist, you simply need to not attempt a connection for a short period of time (see above), or restart the VNC Server software/the computer running VNC Server.

What username and password should I be using?

If you have failed to enter your connection details correctly a large number of times, it's possible they are not correct. Please ensure that you are connecting to the correct VNC Server, and that you are entering the correct username and/or password.

If you are unsure as to the username and password required, please see this article for some suggestions: What username and password do I enter when I'm trying to connect to VNC Server?

Was this article helpful?
68 out of 210 found this helpful


  • It would be helpful to provide more information on the timeout period. I'm working remotely and am unable to login after doing something stupid. Telling my management I do stupid stuff is fine, they know that. Telling them we have to wait "a short period of time" makes me sound like I'm making stuff up. How long does it take, if it's non determinate, then it would be more helpful to know that up front than it would something vague.


    Comment actions Permalink
  • Hi Bryan,

    Thanks for getting in touch. I have updated the article to refer to the timeout which is mentioned in the top section:

    The IP address is initially blocked for 10 seconds, but this doubles for each unsuccessful attempt thereafter.

    The period of time you have to wait will vary, depending on how many failed login attempts you have made.

    Kind regards,


    Comment actions Permalink
  • How do I disable this timeout feature?

    Comment actions Permalink
  • Hi,
    I have a VNC Server that I am trying to connect using VNC Viewer. Despite entering the correct password, it just won't let me login. When I try to connect using another VNC viewer, using the same credentials, it connects just fine. How do I fix it?

    Comment actions Permalink

Please sign in to leave a comment.