USER MODE x

Usage: UMODE +|-x
Usage: MODE <nick> +|-x
x - Hash host
IP masking of the hostmask which helps to prevent denial of service attacks. In the formation of =numbersletters or numbersletter=. You can still ban specific users by their full address, just ban the munged version that you can see in their whois, and they will be unable to join.
Privilege: operator
Examples:
/mode jimmers +x
/umode +x

USER MODE X

Usage: UMODE +|-X
Usage: MODE <nick> +|-X
X - Dehash host
The +X mode will break the +x mode except on channel information or +x for network operators.
Privilege: operator
Examples:
/mode jimmers +X
/umode +X