How to stop ping on imac

If you don't realize that you can stop ping in the Terminal with control+c to interrupt it, or limit its number of pings by specifying ping -c 10, you probably should not be launching the Terminal in the first place.

Maybe he wants to stop is computer from responding to a ping...

Please read the following user tip and restate your question/problem in detail: 

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I don't know either, but if that is the case then Use stealth mode to keep your Mac more secure - Apple Support is applicable.

As the OP has not clarified their circumstance, any guess will do… 😉