After searching, I have found no way to change your password from anywhere within the game.
The save filesThere are REDSHRT2-encrypted, which can (and has) been broken, but finding a (working) toolno external tools to do it may be annoying and/or fruitlesschange the password other than hexediting the actual save files.
For the moment, I'm going to say it's not worth your time to try and change it, especially if it's a valuable password. Just delete and start again.
I'll edit this answer once I find a way to break REDSHRT2 and hexedit the save files.
By the way, Uplink doesn't delete your save files when you retire an agent, it merely moves them to a "deleted" directory, so if you're very concerned, you should delete them manually.
- On Linux your save files are located in
~/.uplink/
asNAME.usr
andNAME.tmp
(replace NAME with your profile name, obviously). - On Windows they should be located in
/Program Files/Uplink/User/
or something similar. - I don't know where they might be on Mac.