Blocking complete subnets...

[opentoe]

For some reason I'm constantly getting hit hard from obsmtp dot com which is a Google IP address. One of the matching IP addresses is 68.18.3.39. I want to completely block anything from 64.18.0.0 and on. Would the correct way to input that into my deny config file be like this?

68.18.0.0/32

Update:
I think I was able to get it.
68.18.0.0/16 I believe blocks all from 68.18.*.*

[Sergio]

This will block all the CIDR range for the IP 68.18.3.39:
68.18.0.0/14
according to:
https://www.countryipblocks.net/search_ ... 68.18.3.39

but be careful you will be blocking hundred of IPs, it is wise to only block /24 range, in your case 68.18.3.0/24