block IP by wildcard

You can’t with a wildcard but you could by using the CIDR range. For instance if you wanted to block 161.123.* (your example wasn’t a valid range since 458 is outside an actual address space) you would enter 161.123.0.0/16.

I used a translator like the one here to compute the CIDR.
https://www.ipaddressguide.com/cidr
I entered 161.123.0.0 as the starting IP and 161.123.255.255 as the ending IP.

You’d enter this on the Firewall > Blocking page on your site. Click on the Custom Pattern tab and enter the CIDR range where it says IP Address range and a reason for the block where it says “Block Reason”. Then click the blue Block Visitors Matching This Pattern” button.

Hope this helps
Tim