Yes, linux is built using C and the GNU compiler which is opensource. Im pretty sure it does c++ as well. I know that to install gcc under Uubntu you install the package "build-essential" but i dont know about Kubuntu. Might be worth a try anyway.
I use codeblocks open source IDE on my (fedora) linux box which works great with Gcc and just about any other compliler out there.
If you want something more "linux-y" you might look into Vim for just messing around with code.
It's not an IDE, but a very fancy editor which is the advanced form of the old Unix Vi . It's not the most user friendly thing in the world, but rather interesting if you don't mind arcane commands. Run vimtutor for a tutorial.
Also, you might have to use the command
g++ -o hello hello.cpp to compile c++ . That's the way it is on my machine, at least.
Thanks for all the suggestions.. does anyone know of any fully integrated development environments, when you can just click a button and it will compile your code by calling the compiler and produce and output by calling the newly created .exe, like Dev-C++ or Visual C++ for examples.. I'm fine using command line, i'm just not used to Linux right now, only used it for a few days, and to be quite honest, I'm lazy :p