Getting suddenly a lot of request from CFNetwork/Darwin

I've noticed in the AWS console that our website got a lot of more requests than normally. Especially in the night hours (Europe time).

Then I've checked the nginx logs and now I know that a lot of devices with different IP addresses request the root of the website, most of them with the user agent swcd (unknown version) CFNetwork/978.0.7 Darwin/18.7.0. Sometimes one of the versions is different.

I have absolutely no idea what is going on so I hope that someone can help.

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