2. How does Nepenthes work?
Nepenthes vulnerability modules require knowledge about weaknesses so one can draft a Dialogue how the virus will exploit the weakness, gain the needed information to download the file and send the attacker just enough information he does not notice he gets fooled.
On the other hand Nepenthes is quite usefull to capture new exploits for old vulnerabilities.
As Nepenthes does not know these exploits, they will appear in the logfiles.
By running these captures against a real vulnerable machine one can gain new information about the exploit and start writing an Nepenthes Dialogue.
2.1 Why would one want to run Nepenthes?
The first argument is, its free. The software is free, the viruses you can capture are free. You can collect this annoying stuff like stamps without paying a diam. The rest of the arguments are security related an discussable. Setting up a host running Nepenthes can improve network security drastically, as you can see who scans for which known vulnerabilities.