Virus, that can be used to dynamically update hostname, with new IP.
First you need to buy a hostname. It really doesn't matter, what the hostname is.
Upload the virus on target PC, and enter the hostname you own, upon instalation.
Now, everytime you connect to the tracked PC just use the hostname you assigned to it.
It is also recommended to use hider to prevent virus deletion. (Of course hide all other viruses, to lower the chances of target running AV)