Internet security

Internet security

Internet security is a branch of computer security[1] specifically related to the Internet. Its objective is to establish rules and measures to use against attacks over the Internet.[2] The Internet represents an insecure channel for exchanging information leading to a high risk of intrusion or fraud, such as phishing.[3] Different methods have been used to protect the transfer of data, including encryption.


Types of security

Network layer security

TCP/IP can be made secure with the help of cryptographic methods and protocols that have been developed for securing communications on the Internet. These protocols include SSL and TLS for web traffic, PGP for email, and IPsec for the network layer security.

IPsec Protocol

This protocol is designed to protect communication in a secure manner using TCP/IP. It is a set of security extensions developed by IETF, and it provides security and authentication at the IP layer by using cryptography. To protect the content, the data is transformed using encryption techniques. There are two main types of transformation that form the basis of IPsec: the Authentication Header (AH) and Encapsulating Security Payload (ESP). These two protocols provide data integrity, data origin authentication, and anti-replay service. These protocols can be used alone or in combination to provide the desired set of security services for the Internet Protocol (IP) layer.

The basic components of the IPsec security architecture are described in terms of the following functionalities:

  • Security protocols for AH and ESP
  • Security association for policy management and traffic processing
  • Manual and automatic key management for the internet key exchange (IKE)
  • Algorithms for authentication and encryption

The set of security services provided at the IP layer includes access control, data origin integrity, protection against replays, and confidentiality. The algorithm allows these sets to work independently without affecting other parts of the implementation. The IPsec implementation is operated in a host or security gateway environment giving protection to IP traffic.

Electronic mail security (E-mail)


Email messages are composed, delivered, and stored in a multiple step process, which starts with the message's composition. When the user finishes composing the message and sends it, the message is transformed into a standard format: an RFC 2822 formatted message. Afterwards, the message can be transmitted. Using a network connection, the mail client, referred to as a mail user agent (MUA), connects to a mail transfer agent (MTA) operating on the mail server. The mail client then provides the sender’s identity to the server. Next, using the mail server commands, the client sends the recipient list to the mail server. The client then supplies the message. Once the mail server receives and processes the message, several events occur: recipient server identification, connection establishment, and message transmission. Using Domain Name System (DNS) services, the sender’s mail server determines the mail server(s) for the recipient(s). Then, the server opens up a connection(s) to the recipient mail server(s) and sends the message employing a process similar to that used by the originating client, delivering the message to the recipient(s).

Pretty Good Privacy (PGP)

PGP provides confidentiality by encrypting messages to be transmitted or data files to be stored using an encryption algorithm such 3DES or CAST-128. Email messages can be protected by using cryptography in various ways, such as the following:

  • Signing an email message to ensure its integrity and confirm the identity of its sender.
  • Encrypting the body of an email message to ensure its confidentiality.
  • Encrypting the communications between mail servers to protect the confidentiality of both the message body and message header.

The first two methods, message signing and message body encryption, are often used together; however, encrypting the transmissions between mail servers is typically used only when two organizations want to protect emails regularly sent between each other. For example, the organizations could establish a virtual private network (VPN) to encrypt the communications between their mail servers over the Internet.[4] Unlike methods that can only encrypt a message body, a VPN can encrypt entire messages, including email header information such as senders, recipients, and subjects. In some cases, organizations may need to protect header information. However, a VPN solution alone cannot provide a message signing mechanism, nor can it provide protection for email messages along the entire route from sender to recipient.

Multipurpose Internet Mail Extensions (MIME)

MIME transforms non-ASCII data at the sender's site to Network Virtual Terminal (NVT) ASCII data and delivers it to client's Simple Mail Transfer Protocol (SMTP) to be sent through the Internet.[5] The server SMTP at the receiver's side receives the NVT ASCII data and delivers it to MIME to be transformed back to the original non-ASCII data.

  • Secure/Multipurpose Internet Mail Extensions (S/MIME)

S/MIME provides a consistent means to securely send and receive MIME data. S/MIME is not only limited to email but can be used with any transport mechanism that carries MIME data, such Hypertext Transfer Protocol (HTTP).[6]

Message Authentication Code

A Message Authentication Code is a cryptography method that uses a secret key to encrypt a message. This method outputs a MAC value that can be decrypted by the receiver, using the same secret key used by the sender. The Message Authentication Code protects both a message's data integrity as well as its authenticity.[7]


A firewall controls access between networks. It generally consists of gateways and filters which vary from one firewall to another. Firewalls also screen network traffic and are able to block traffic that is dangerous. Firewalls act as the intermediate server between SMTP and HTTP connections.

Role of firewalls in Internet security

Firewalls impose restrictions on incoming and outgoing packets to and from private networks. All the traffic, whether incoming or outgoing, must pass through the firewall; only authorized traffic is allowed to pass through it. Firewalls create checkpoints between an internal private network and the public Internet, also known as choke points. Firewalls can create choke points based on IP source and TCP port number. They can also serve as the platform for IPsec. Using tunnel mode capability, firewall can be used to implement VPNs. Firewalls can also limit network exposure by hiding the internal network system and information from the public Internet.

Types of firewalls

Packet filters

Packet filters are one of several different types of firewalls that process network traffic on a packet-by-packet basis. Their main job is to filter traffic from a remote IP host, so a router is needed to connect the internal network to the Internet. The router is known as a screening router, which screens packets leaving and entering the network.

Circuit-level gateways

The circuit-level gateway is a proxy server that statically defines what traffic will be allowed. Circuit proxies always forward packets containing a given port number, provided the port number is permitted by the rules set. This gateway operates at the network level of an OSI model. The main advantage of a proxy server is its ability to provide Network Address Translation (NAT), which can hide the user's IP address from the Internet, effectively protecting all internal information from the Internet.

Application-level gateways

An application-level gateway is a proxy server operating at the TCP/IP application level. A packet is forwarded only if a connection is established using a known protocol. Application-level gateways are notable for analyzing entire messages rather than individual packets of data when the data are being sent or received.

Malicious software and antivirus


Commonly, a computer user can be tricked or forced into downloading software onto a computer that is of malicious intent. Such programs are known as malware and come in many forms, such as viruses, Trojan horses, spyware, and worms. Malicious software is sometimes used to form botnets.


Viruses are programs that can replicate their structures or effects by infecting other files or structures on a computer. The common use of a virus is to take over a computer to steal data.

Trojan horse

A Trojan horse (commonly known as a Trojan) is a general term for malicious software that pretends to be harmless so that a user willingly allows it to be downloaded onto the computer.


The term spyware refers to programs that surreptitiously monitor activity on a computer system and report that information to others without the user's consent.


Worms are programs that can replicate themselves throughout a computer network, performing malicious tasks throughout.


A botnet is a network of "zombie" computers that have been taken over by a "bot" that performs large-scale malicious acts for the creator of the botnet.


Antivirus programs and Internet security programs are useful in protecting a computer or programmable device from malware.

Such programs are used to detect and usually eliminate viruses; however, it is now common to see security suites, containing also firewalls, anti-spyware, theft protection, and so on to more thoroughly protect users.[8]

Traditionally, a user would pay for antivirus software; however, computer users now can, and do, download from a host of free security applications on the Internet.[9]

Denial-of-service attack

A denial-of-service attack (DoS attack) or distributed denial-of-service attack (DDoS attack) is an attempt to make a computer resource unavailable to its intended users. Although the means to carry out, motives for, and targets of a DoS attack may vary, it generally consists of the concerted efforts of person or persons to prevent an Internet site or service from functioning efficiently or at all, temporarily or indefinitely.

Browser choice

Web browser statistics tend to affect the amount a Web browser is exploited. For example, Internet Explorer 6, which used to own a majority of the Web browser market share,[10] is considered extremely insecure[11] because vulnerabilities were commonly exploited due to its former popularity. Now, however, browser choice is more evenly distributed (Internet Explorer at 22.9%, Firefox at 39.7%, Google Chrome at 30.5%, and so on);[10] vulnerabilities are commonly exploited in many browsers.[12][13][14] Apple's web browser, Safari, is the fourth most popular web browser. Although it is only 4% of the total browser usage, it too has many vulnerabilities.[15][16]

Buffer overflow attacks

A buffer overflow is an attack that could be used by a cracker to get full system access through various methods by essentially cracking a computer using brute force. Most security applications and suites are incapable of adequate defense against these kinds of attacks.

See also


Guidelines on Electronic Mail Security

  1. ^
  2. ^ Gralla, Preston (2007). How the Internet Works. Que Pub, Indianapolis. ISBN 0789721325.
  3. ^ Rhee, M. Y. (2003). Internet Security: Cryptographic Principles,Algorithms and Protocols. Chichester: Wiley. ISBN 0470852852.
  4. ^ Virtual Private Network
  5. ^ Network Virtual Terminal
  6. ^
  7. ^
  8. ^ Rebbapragada, Narasu. All-in-one Security. Retrieved 19 November 2010.
  9. ^ Larkin, Eric. Build Your Own Free Security Suite. Retrieved 19 November 2010.
  10. ^ a b Browser Statistics. Retrieved 1 August 2011.
  11. ^ Bradly, Tony. "It's Time to Finally Drop Internet Explorer 6" . Retrieved 19 November 2010.
  12. ^ Messmer, Ellen and NetworkWorld. "Google Chrome Tops 'Dirty Dozen' Vulnerable Apps List". Retrieved 19 November 2010.
  13. ^ Keizer, Greg. Firefox 3.5 Vulnerability Confirmed. Retrieved 19 November 2010.
  14. ^ Skinner, Carrie-Ann. Opera Plugs "Severe" Browser Hole. Retrieved 19 November 2010.
  15. ^
  16. ^

External links

Wikimedia Foundation. 2010.

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