Risk: Informational
In a survey conducted by Insecure.org, 3243 IT security professionals were asked to name their favourite freely available network tools and NTA's ike-scan was 53rd out of 100.
The survey has been running since 2000 and is conducted every three years. Ike-scan is a new entrant for 2006 and its ranking is testament to its popularity and success.
Ike-scan exploits transport characteristics in the Internet Key Exchange (IKE) service, the mechanism used by VPNs to establish a connection between a server and a remote client. It scans IP addresses for VPN servers by sending a specially crafted IKE packet to each host within a network. Most hosts running IKE will respond, identifying their presence. The tool then remains silent and monitors retransmission packets. These retransmission responses are recorded, displayed and matched against a known set of VPN product fingerprints.
You can see all the tools cited in the survey at http://sectools.org/