Self-explanatory. Hacking a bank in Uplink to locate accounts to hack into and steal funds from.
I did all of this off of a basic Gateway within the first several weeks of ingame time after starting a new game.
The only thing I upgraded was the processor, I believe to a 100-160 Ghz, to make decyphering a tad bit faster.
There are two methods to doing this. In this one I chose to hack into the bank and locate accounts to check out through administration. Another method, which is actually much easier, is to find accounts by doing the "trace account" missions you can get from the Uplink ISS. Those generally have accounts involved with high balances and/or recent transactions of high amounts.