Site to Site VPN, Remote VPN

A virtual private network (VPN) is a private network that interconnects remote (and often geographically separate) networks through primarily public communication infrastructures such as the Internet. VPNs provide security through tunneling protocols and security procedures such as encryption. For example, a VPN could be used to securely connect the branch offices of an organization to a head office network through the public Internet. A VPN can also be used to interconnect two similar-type networks over a dissimilar middle network for example, two IPv6 networks over an IPv4 network.
There are two main types of VPN: remote-access VPNs and Site-to-site VPNs.
Remote-access VPNs allow individual users to connect to a remote network such as roaming salespeople connecting to their company's intranet.
Site-to-site VPNs allow inter-connection of networks of multiple users for example, branch offices to the main company network. VPNs hence reduce costs as they eliminate the need for dedicated leased lines between networks, but instead use existing infrastructures to connect networks while adding a layer of security.

Intranet-based
It is when there are one or more remote locations that wish to join in a single private network, they can create an intranet VPN to connect each separate LAN to a single WAN.

Extranet-based
Extranet-based is like connecting LANs together. This extranet VPN allows different intranet to work together in a secure, shared network environment while preventing access to their separate intranets.

Client software
This software is require for people who wants to use VPN from their computers. This is needed to  establish and maintain a connection to the VPN.The client software sets up the tunnelled connection to a NAS, which the user indicates by its Internet address. The software also manages the encryption required to keep the connection secure.

IPSec (ESP, AH, DES, MD5, SHA, DH)

Internet Protocol security (IPSec) is a framework of open standards for helping to ensure private, secure communications over Internet Protocol (IP) networks through the use of cryptographic security services. IPSec supports network-level data integrity, data confidentiality, data origin authentication, and replay protection. Because IPSec is integrated at the Internet layer (layer 3), it provides security for almost all protocols in the TCP/IP suite, and because IPSec is applied transparently to applications, there is no need to configure separate security for each application that uses TCP/IP.
The examples of IPsec are ESP, AH, DES, MD5, SHA, and DH.

IPSec helps provide defense-in-depth against:
• Network-based attacks from untrusted computers, attacks that can result in the denial-of-service of applications, services, or the network
• Data corruption
• Data theft
• User-credential theft
• Administrative control of servers, other computers, and the network.

Authentication Headers (AH)
AH provides connectionless integrity and data origin authentication for IP datagrams and provides protection against replay attacks.
Encapsulating Security Payloads (ESP)
ESP provide confidentiality, data-origin authentication, connectionless integrity, an anti-replay service (a form of partial sequence integrity), and limited traffic-flow confidentiality.

Data Encryption Standard(DES)
DES is a widely-used method of data encryption using a private (secret) key . DES applies a 56-bit key to each 64-bit block of data. The process can run in several modes and involves 16 rounds or operations.
Message Digest 5(MD5)
MD5 is a widely used cryptographic hash function with a 128-bit hash value. MD5 is widely used in security-related applications, and is also frequently used to check the integrity of files. MD5 value of file is considered to be a highly reliable fingerprint that can be used to verify the integrity of the file's contents. If as little as a single bit value in the file is modified, the MD5 value for the file will completely change. Forgery of a file in a way that causes MD5 to generate the same result as that for the original file is considered to be extremely difficult.
SHA
The Secure Hash Algorithm is one of a number of cryptographic hash functions published by the National Institute of Standards and Technology (NIST) as a U.S. Federal Information Processing Standard (FIPS):
Diffie-Hellman(DH)
The protocol has two system parameters p and g. They are both public and may be used by all the users in a system. Parameter p is a prime number and parameter g (usually called a generator) is an integer less than p, which is capable of generating every element from 1 to p-1 when multiplied by itself a certain number of times, modulo the prime p. However, it is vulnerable to a middleperson attack.
Security Associations (SA)
SA provides the bundle of algorithms and data that provide the parameters necessary to operate the AH and/or ESP operations. The Internet Security Association and Key Management Protocol (ISAKMP) provides a framework for authentication and key exchange, with actual authenticated keying material provided either by manual configuration with pre-shared keys, Internet Key Exchange (IKE and IKEv2), Kerberized Internet Negotiation of Keys (KINK), or IPSECKEY DNS records.

Public Key Infrastructure (Digital Cert)

PKI is a security architecture that has been introduced to provide an increased level of confidence for exchanging information over an increasingly insecure Internet.  Public key cryptography uses a pair of mathematically related cryptographic keys.   If one key is used to encrypt information, then only the related key can decrypt that information. 
A certificate is information referring to a public key, that has been digitally signed by a Certification Authority (CA).  Certificates conforming to that standard include information about the published identity of the owner of the corresponding private key, the key length, the algorithm used, and associated hashing algorithm, dates of validity of the certificate and the actions the key can be used for. The CA takes responsibility for identifying (to a stated extent) the correctness of the identity of the person asking for a certificate to be issued, and ensures that the information contained within the certificate is correct and digitally signs it.

Applications that use PKI:

• ·         Digital signatures
• ·         Smart card logon
• ·         Secure e-mail
• ·         Software code signing
• ·         IP Security (IPSec)
• ·         Software restriction policy
• ·         Internet authentication
• ·         Encrypting File System
• ·         PKI consist of a few components which are closely related together:
• ·         Certificate and CA management tools
• ·         Certification Authority (CA)
• ·         Registration Authority (RA)
• ·         Validation Authority (VA)
• ·         Attribute Authority (AA)
• ·         Attribute Certificates
• ·         Certificate Template
• ·         Digital Certificate
• ·         PKI enabled applications and services

Authentication, Authorization and Accounting

Authentication, authorization, and accounting (AAA) is a security architecture for distributed distributed systems, which enables control over which users are allowed access to which services, and how much of the resources they have used.

The process of authentication is based on each user having a unique set of criteria for gaining access. The AAA server compares a user's authentication credentials with other user credentials stored in a database. If the credentials match, the user is granted access to the network. If the credentials are at variance, authentication fails and network access is denied. Examples of types of credentials are passwords, one-time tokens, digital certificates, and phone numbers (calling/called).

After authentication, a user must gain authorization  for doing certain tasks. After logging into a system, for instance, the user may try to issue commands. The authorization process determines whether the user has the authority to issue such commands. Simply put, authorization is the process of enforcing policies: determining what types or qualities of activities, resources, or services a user is permitted. Usually, authorization occurs within the context of authentication. Once you have authenticated a user, they may be authorized for different types of access or activity. Examples of types of service include, but are not limited to: IP address filtering, address assignment, route assignment, quality of Service/differential services, bandwidth control/traffic management, compulsory tunneling to a specific endpoint, and encryption.

The final process is accounting, which measures the resources a user consumes during access. This can include the amount of system time or the amount of data a user has sent and/or received during a session. Accounting is carried out by logging of session statistics and usage information and is used for authorization control, billing, trend analysis, resource utilization, and capacity planning activities.

Reference:
http://searchsecurity.techtarget.com/definition/authentication-authorization-and-accounting
http://en.wikipedia.org/wiki/AAA_protocol

Context-based access control

Context-based access control (CBAC) intelligently filters TCP and UDP packets based on application layer protocol session information that are not specifically denied by an ACL and can be used for intranets, extranets and internets. CBAC can be configured to permit specified TCP and UDP traffic through a firewall only when the connection is initiated from within the network needing protection.
With CBAC inspection rules, you can configure alerts and audit trail information on a per-application protocol basis. It generates real-time alerts and audit trails. Audit trails uses system log to track all the networking transaction. It can also mitigate Denial of Service (Dos) and detection which is essential for every computer.
CBAC inspects traffic that travels through the firewall to discover and manage state information for TCP and UDP sessions. This state information is used to create temporary openings in the firewall's access lists to allow return traffic and additional data connections for permissible sessions.




Every computer will have access to network, regarding work, surfing internet and so on. CBAC will check every packets that is in traffic. With CBAC, CBAC can examines the application-layer protocol information to learn about the state of TCP or UDP session. This ensures that our application are not downloading or allowing people to gain access to our computer through these applications.

Access list control

An access control list (ACL) is a table that tells a computer operating system which access rights each user has to a particular system object, such as a file directory or individual file. Each object has a security attribute that identifies its access control list. The list has an entry for each system user with access privileges. The most common privileges include the ability to read a file (or all the files in a directory), to write to the file or files, and to execute the file (if it is an executable file, or program).








Different Operating System (OS) may use different Access Control List. When a user wants to initiate a specific action against a component item (for example, edit an article), the system checks the permission for this combination of user, item, and action. If it is allowed, then the user can proceed. Otherwise, the action is not allowed.
Allow: Allows this action for this level and group and for lower levels and child groups. This does not have any effect if a higher group or level is set to Deny or Allow. If a higher group or level is set to Deny, then this permission will always be denied. If a higher group or level is set to Allow, then this permission will already be allowed.
Deny: Denies this action for this level and group.
Access control list may include networking Access Control List (ACL), filesystem ACL and etc.







Reference:
http://en.wikipedia.org/wiki/Access_control_list
http://searchsoftwarequality.techtarget.com/definition/access-control-list

Secure Perimeter Routers & Disable Services & Logging

The first line of defense against security threat is usually: Perimeter router, includes configuration of the perimeter. By disabling services and logging, network security can be more secure.
Some services which are rarely used like: CDP, finger, and TCP and UDP can be disable to secure the network even further. Hackers might make use of these service's security issue to try and gain unauthorized access into the network or get the network information.
Event logging is also important for security purpose, to reference is any security issues 'pop' out.
Interface status change, changes to system configuration, access list matches, events detected by the firewall, and intrusion detection features are some things that are log. Most routers are able to save system
logging information to a local RAM buffer.
There are different types of router configuration. Patches & Updates which means we have to stay updated to the latest patch and update. Protocols which means by using ingress and egress filtering, or screen ICMP traffic from internal network to counter protocol level attack. Administrative access which means deciding which interface and ports administration connection is allowed.  Restricting access to the specific interfaces and ports, and encrypting them, having countermeasures against hijacking into these interfaces.