To use the free trial of Nessus, you need an email address to receive an activation key.
There are two modes to activate a Nessus server:
- Online mode registration
If the computer running Nessus server has internet, you can activate the software by entering the activation key. It will authorize the use only if the right key is entered.
- Offline mode registration
If you don't have internet on the computer running Nessus server, you need to activate the software with a license:
- On the Nessus server, check the box "Register offline". It will display a challenge.
- With another computer having internet access, go to this page to generate a license to use the software. It will require the challenge generated by the offline Nessus server and the activation key received by mail during registration.
- Copy the license generated by the website to the offline Nessus server to authorize the use of the software.
To avoid users bypassing the registration step through offline mode, it requires the activation key received by email before receiving the license needed to activate the software.
How can an "offline" challenge authentication be secure?
If challenges and responses are already generated before downloading the software, users can gather all the challenges and the responses in a list. At some point, all the challenges will exist in this list and no one will need to register by mail to get an activation key to have the response of the challenge.
