Why do I receive an error message saying "Too many security failures" when I try to connect?


What causes this message?

VNC Server has a blocklist 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. This is built in to VNC Server and does not rely on operating system support.

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

How do I reset the timeout?

To reset the blocklist, 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.

A successful connection from an IP address also resets the blocklist timeout.

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?

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  • 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.


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  • 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,


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  • How do I disable this timeout feature?

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  • 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?

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