weenie,
IP addresses are not as easily spoofed as you make it sound and even more so if it is a TCP connection and not UDP. The first thing that needs to happen is you have to be able to guess the sequencing numbers. This is because a packet needs to correctly identify itself or it is a bust. This has been getting harder and harder, but is still possible. You also need to make sure the spoofed machine is not able to reply. This is because the packets going to the spoofed machine will cause a RST packet to be sent (hey - I have no idea what you are talking about - I didn't initiate a session with you). This is usually done by a denial of service attack in conjunction with the spoofing. Finally, since you won't be seeing the packets come back - you will need to know the proper sequence to send your commands. SMTP is pretty well defined for this, but trying to telnet into someone's machine using a spoofed IP address is nearly impossible.

Now if you have gained access to the spoofed target, you are asking for trouble since where do you think the first place they are going to look is?

If you have a wire tap on the victim machine's network - why are you bothering to spoof in the first place?

I am not 3l33t nor am I a script kiddy - but I do know that it is not as trivial as you make it out to be.

Cheers - L~R