x - Hash or Mangle:
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.
/mode Dan +x
X - de Hash:
The +X mode will break the +x mode except on room information or +x for network operators.
/mode Dan +X