You can always use a key logger as a security tool. If you run a network and want to know what all the people on all the computers are doing, you can use a key logger to find out. So, you could find a key logger at the right place with the right words, easily. Just like Trojans, if you use a Trojan to transfer files, which they were meant for in the first place(when DCC through serial ports are not applicable), you could also get one at the right location for the right reasons.