You have tried to connect with a network that could pose a threat your security. Your security software will identify these networks as either risky or dangerous.
Risky
"Open" networks do not require authentication to connect with
them, so anyone can use them. With this greater ease of access
comes a higher chance that strangers could try to snoop on what you
send and receive through these networks. You should try not to use
risky networks if possible.
Dangerous
When you connect to a network, your computer will normally contact
an authentication server. This server should have a reliable
security certificate to help ensure that nobody else intercepts the
data that you send and receive through the network.
If the authentication server has an expired, fake, or otherwise
untrustworthy security certificate, then your connection could be
hijacked or monitored without your knowledge. For your own safety,
you should avoid networks identified as dangerous.
Try to connect with a more trustworthy network instead of the one that triggered the warning.
If you still want or need to use a risky or dangerous network, you can click the Trust this network despite the risk or Trust this network despite the danger link under the OK button. Clicking the link adds the network to an exception list, so that you will no longer receive warnings about it.
You can also remove the network from the exception
list if you change your mind about it later.