Which Intrusion Detection System is best applicable for large environments where critical assets on the network need extra security and is ideal for observing sensitive network segments?

Which of the following techniques does a vulnerability scanner use in order to detect a vulnerability on a target service?

Which of the following types of jailbreaking allows user-level access but does not allow iboot-level access?

You receive an e-mail like the one shown below. When you click on the link contained in the mail, you are redirected to a website seeking you to download free Anti-Virus software.
Dear valued customers,
We are pleased to announce the newest version of Antivirus 2010 for Windows which will probe you with total security against the latest spyware, malware, viruses, Trojans and other online threats. Simply visit the link below and enter your antivirus code:

or you may contact us at the following address:
Media Internet Consultants, Edif. Neptuno, Planta
Baja, Ave. Ricardo J. Alfaro, Tumba Muerto, n/a Panama
How will you determine if this is Real Anti-Virus or Fake Anti-Virus website?

An attacker is using nmap to do a ping sweep and a port scanning in a subnet of 254 addresses.
In which order should he perform these steps?