Warning W518 - Wireless adapter in ad-hoc mode.
Fix: Your wireless adapter is set to ad-hoc (device to device) mode. This allows other computers to connect to your computer. If this is what you want to do, ignore this warning, otherwise turn it off. This would allow malicious users to attempt to connect to your computer via the wireless ad-hoc network it offers to hack into your computer.
Check your system (Wireless \ Advanced) to turn off ad-hoc network mode.
For more information, please see the (FAQ).