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VPN Interview - August
20, 2008, 17:00 pm by Rajmeet Ghai
What is Trusted and Untrusted Networks?
Answer
Trusted networks: Such
Networks allow data to be transferred transparently. The
machines using a trusted network are usually
administered by an Administrator to ensure that private
and secured data is not leaked. Access to this network
is limited. Computers using trusted networks are more
secured and confidential because of strong firewalls.
Untrusted networks: Such networks
are usually administered by the owners. They can allow
improper access to sensitive or personal data. These
machines are usually separate. Such machines could me
more prone to attacks.
What is VPN?
Answer
Virtual Private network is
a network that used the public telecommunication
infrastructure. This means that it used public wires to
connect the nodes. E.g. Internet. VPN supports remote
access to computers and allow data to be transmitted
over this public network. Even though the data is
transmitted over a public network, encryption and
decrypting data to ensure security.
What are the different types of VPN?
Answer
- Remote Access VPN:- Also
called as Virtual Private dial-up network (VPDN) is
mainly used in scenarios where remote access to a
network becomes essential. Remote access VPN allows
data to be accessed between a company’s private
network and remote users through a third party service
provider; Enterprise service provider. E.g Sales team
is usually present over the globe. Using Remote access
VPN, the sales updates can be made.
- Site to Site VPN –
Intranet based: This type of VPN can be used when
multiple Remote locations are present and can be made
to join to a single network. Machines present on these
remote locations work as if they are working on a
single network.
- Site to Site VPN – Extranet
based: This type of VPN can be used when several
different companies need to work in a shared
environment. E.g. Distributors and service companies.
This network is more manageable and reliable.
What are the different authentication methods used
in VPNs?
Answer
The authentication method
uses an authentication protocol. The methods are:
- EAP authentication method: Extensible authentication protocol
authenticates remote access connection. The
authentication mechanism is decided between the remote
VPN client and authenticator (ISA). The mechanism is
typical in which authenticator requests for
authentication information and the responses are given
by the remote VPN client.
- MS Chap Authentication method: Microsoft Challenge Handshake
Authentication Protocol (MS-CHAP) starts with the
authenticator (Remote access server) challenge. The
challenge to the remote access client sends a session
identifier and challenge string. The client in
response sends the nonreversible encryption of the
string, the identifier and password. Authenticator
checks the credentials and grants access on a
successful authentication.
- Unencrypted passwords (PAP):- Uses plain text passwords. Does not
involve encryption. Used for less secure clients.
- Shiva Password Authentication Protocol
(SPAP):- It is a password authentication
protocol. It is less secure as the same user password
is always sent in the same reversibly encrypted
form
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