I don't know but I think it is a paradox.

Here is why:

You put up a firewall to make you secure. So you should be secure. But by putting up a firewall you fail to secure something else or you are lax in another area of security. Because you think "it's been take care of. So I see it as a paradox. Although it could be ironic if someone put up a firewall but then was hacked because of something they didn't do thinking they didn't need it if they had a firewall. That would be an irony.