For some values of "simple", some values of "long", and some values of "enough".

In other words, impossible.

Onkel Paul

Simple? Yes.
In a month? Theoretically impossible.

If you were to combine the computational power of every supercomputer, every computer, every laptop and tablet, every cell phone, every TI 89 calculator, every abacus, and every person on the planet with pencil and paper trying to guess the private key of a certain Bitcoin address would take so incredibly long that you, nor anyone else, could begin to fathom that amount of time.

Let's look at the math...

There are 2¹⁶⁰ possible addresses. That's 1,461,501,637,330,902,918,203,684,832,716,283,019,655,932,542,976 addresses. Now there are ASIC miners that can compute 1 trillion SHA-256 hashes per second, so I can imagine an ASIC machine that could compute 1 trillion bitcoin addresses per second. That's 1,000,000,000,000 addresses per second. With that device, you could crack most of the 2¹⁶⁰ possible addresses in about 1,461,501,637,330,902,918,203,684,832,716,283,020 seconds, or about 1,112,253,909,688,662,799,241,769,279,083 years.

Now, to be fair, you don't have to crack every address -- just the ones with the coins. I believe there are about 200,000 addresses with a non-trivial amount of BTC. With the device I described above, you could crack one of those addresses every 5,561,269,548,443,313,996,208,846 years, not once a month.