It's been a long time since I played, so things might have changed since then, but back in the day there was a way to make the game ridiculously easy (that some people may consider cheating, so if you don't want to ruin the game, stop reading).
IIRC, there is a public IP directory you can access right from the start of the game (either it's in your list of starting IPs, or it's some constant address that doesn't change from game-to-game). Accessing this at the start of the game will give you all the IPs you will ever need - simply route every hack-attempt through every IP listed there.
I remember doing this on my second play-through, and getting very bored because you get 600+ seconds for every hack attempt, allowing you to hack even difficult targets with a low-powered PC.