SECURITY IN COMPUTER NETWORKS

In this article it presents the electronic security of the computer networks. The electronic security refers to the totality of the policy recomandations and actions required to minimize the risk associated to perform electronic transactions, the risk refers to branches in the system, intrusion or theft of any means, technique or process used to protect imformation system. The confidentiality, integrity, availability, and compliance with laws, regulations and standards are fundamental security objectives, which are among the requirements of a business environment. The security requirements that must be fulfilled for e-business environment are: identification, authentication, accountability and audit. Security audit records dealing with the analysis of the activities performed if the protection system is in accordance with established security policies and procedures. ISO (International Standards Organization) established the security services based on a set of security mechanisms that can be implemented in all protocols OSI (Open Standard Interconnection) to achieve integrity and protection of environmental resources for network communication. The main services defined by ISP are: authentication, access control, data confidentiality, data integrity, non-repudiation and auditing. To fulfill security services exist security mechanisms,that can be used individually or in combination, such as: encryption, digital signatures, access control mechanisms (the list of access rights, passwords, access time test, data integrity mechanism. Software resources mechanism for risk analysis systems are: -OCTAVE (Operationally Critical, Threat, Asset and Vulnerability Evaluation); -COBRA (Consultative, Objective and Bi-functional Risk Analysis)-provides a framework for risk analysis based on ISO 17799 standard (BS 7799) . Among symmetric key cryptographic systems are mentioned: DES, Triple DES, IDEA, FEAL, RC2, RC4 and A5. The active type attacks are: -the attack in force (brute force); -masquerading; -the replay of the packets; -message modification; -unauthorized access via the Internet or web services that are based such as: e-mail, SMTP (Simple Mail Transfer Protocol); -bombs and spams e-mails; -deception by e-mail (e-mail spoofing); -infection; -trojan? (trojan horse); -virus; -worm; -logic bomb; -a certain level of protection and security can be assured by one or more solutions. Among symmetric key cryptographic systems are mentioned: DES, Triple DES, IDEA, FEAL, RC2, RC4, and A5. The electronic signature is the digital form of handwritten signatures- with the same features and capabilities (enables authentication of an electronic document). Extended electronic signature is the signature while satisfying the following conditions: 1.The signature is uniquely linked to the signature; 2.To identify exclusively controlled by means of the signatory; 3. The extended; The PKI Systems are implemented in network protocol documentation: 1.S/MIME( Secure/Multipurpose Internet Mail Extensions); 2.SET(Secure Electronic Transaction); 3.SSL (Secure Socket Layer)-was developed by NetScape to secure the transfer of information between client-server applications such as the Internet. It represents a protocol independent from protocol and application. It provides services of authentication, data compression, encryption and data integrity. The main purpose of the SSL is the secure and the connection between of two applications. Appeal to notions of digital signatures and certification, which does not allow listening, eavesdropping or falsifying the information change between the two parts. IPSEC is a set of application for services integration and Privacy authentication based cryptography IP. The Standard can be used to build virtual private networks (VPN) over the Internet. PPP (Point to Point Protocol) uses features of the ISP dial-up. PPP it uses features of the ISP and the ISP dial-up. PPP and IP packet standard serial lines transmissions between two points: for begin using two protocols. -PAP (Password Authentication Protocol); -CHAP (Challenge HandShake Authentication Protocol) based on encryption. The firewall is the generic name of a component of a network that controls the traffic between the Personal Computer networks of organizations and external networks, for utilization of network policies.The main functions of a firewall are: -block the access of particular websites in the Internet; -limit the traffic of the public services of the organizations (taking into account IP address and ports); -interdicts to some users the access of some servers and external networks; -monitors communications between the internal network and external network; -through encrypts the transmitted packets through VPN networks. 1.The degree of vulnerability A has the following consequences-unconditional access of some bad intentioned users. 2.The degree of vulnerability B allows to local users in general to increase their privileges and to obtain the control over the system. 3.The degree of vulnerability C allows to users to alter indoor or outdoor machining processes. Obvious, is the absence of independent sources stabilized power supply UPS( Uninterruptible Power Supply) which can lead to loos of files to work even damage computer systems in case of high frequency fluctuations or power supply and even certain licenses purchased for a single installation. One of the biggest threats to information security in computer systems is the viruses into systems that infestation so called computer viruses. The general concept of computer virus is describing different types of attacks on computers alter or destroy computer data, but can cause malfunctions in the network by using its resources for self-production. A computer virus is a malicious code a potential harmful piece of software that copies itself into other programs and modify them in order to failure. A worm is an independent of the program. It produces by self-copying from one computer to another network in most cases. While a virus, a worm does not alter or destroy computer data, but can cause malfunctions in the network by using its resources for self-production. It’s multiply using a file transfer mechanisms, such as Internet or e-mail. A Trojan horse (sometimes using the simple name Trojan) is a piece of code that hides inside a program and will run an operation hidden. Spoofer represents a generic name given to programs that allow to a user using some artifices of calculations, have access to information in the system. In general, spoofer they are possibly by suing mechanisms that enable Trojan horse programs that allow access information. A information in the system. Hoax (Joker) are messages sent by e-mail with lose warning about existing virus and requires all persons known to be altered. The most behavior of malicious virus programs with “standard” can be grouped into several categories, depending on the “host” carrier. Viruses meet are: 1.file viruses; 2.boot viruses 3.macro viruses 4.script viruses 5.e-mail viruses 6.chat and instant messaging viruses