This type of info/attacks can be pretty common. If your company/resources are available on the internet then you will see attacks against them. The good news here is that you have put controls in place to block such attacks :)

With that said, yes, you can configure FMC to completely block those IP addresses. You can even create a rule that blocks IPs based on geolocations. For instance, you can block China or even Asia all together if you know for a fact that your company does not have any business ties with that country/continent. 

Now while this may sound like a good idea it does have some pitfalls. For instance, hackers often use proxies and VPNs to hide their original IPs. Others may use infected/compromised machines to launch their attacks. Thus, you might end up blacklisting legitimate IPs/businesses. Also, geolocation information is not always accurate. Thus, even though FMC is showing that the IP is based out of China, it could very well be based out of Singapore :)

So, my recommendation here is to monitor those alerts in FMC. If you have IPs that have multiple hits through extended period of time then you can configure a rule to completely block those. You can also gather information about the IP and report it to the "abuse" department of the ISP hosting it. 

I hope this helps!

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