Mac OS X 10.1.4, the fourth update to Mac OS X 10.1 "Puma", was released on April 17, 2002. It mainly has a build number of 5Q125, although its build number as a Mac OS preinstalled on new Macs can vary: for iMac G4s, it's either 5R48 or 5T91; DVI PowerBook G4s have build 5R60; and eMacs get 5R106.
Network-wise, improvements and enhancements seen include those for PPP-based dialup connections (they are now more reliable and the system more responsive). File searching on local and remote volumes has also been enhanced. In addition, AFP services can now be browsed on networks with 3Com routers. Security-wise, a security update now enables BSD-based TCP/IP connects to check, and bload, broadcast or multicast IP addresses.