Computer networks and security

Understanding of the importance of telecommunication on developing and developed countries and rapid increasing demand of business world's communication has contributed digital communication the most important platform. The telecommunication has been changed from analog to digital form because of the technological improvements on sound quality, high speed data transmission, low data loss. Computer networks have been developed to provide instutional and personel communication. The basics of computer networks have been started with the communication of military computers. For example, the ethernet technogy that has been developed by DLX (Digital Intel Xerox) is a standart now. Nowadays, the ethernet technology, LAN, is being used very popular because of the cost, and easy deployment. The other technogies are Token Ring, lOOVG-AnyLAN and FDDI. LANs can not connect long distances. For this reason, the other technogy, WAN, has been developed. The WAN technogies are ADSL, ISDN, Frame Relay, and ATM. The security problems increased as internet has become most popular platform, and also online shopping and online banking services have most ratings. For this reason, the networks are more vulnerable now. Because of the vulnerabilities on networks the companies have had severe damages, and more downtimes on production environments. Computer viruses, DoS (Denial of Service) attacks, and company computer users' faults are still most important danger. Because of this security concerns, the security devices and programs are developing and using more than ever now. A company must make security policies known before setup the security system. These security policies are, which security devices how often will be used, which roles will be deployed, how to fullfil password management, and physical management of the system, etc. Firewalls and IDSs are the most used products on companies today. After the setup of security system, the tests of the system must be took in place. Then, Systems Engineer have to realize the system regarding the test results, take the correct aciton and monitor the system everytime. xivCommon usage of the Internet in the world has inreased the potential of security threats. As a result of this, there has been important information losses, privacy can be comprimised, or there has been long time downtimes. In the end, those security vulnerabilities can affect people's trust to the Internet and as a result those companies who have internet based gone to end. Finally, Companies have to increase theirsecurity levels gradually, and continue to their investments about preventing new threats. Keywords: Computer Networks, Network, LAN, Token Ring, lOOVG-AnyLAN, Jetonlu Yol, FDDI, WAN, ADSL, ISDN, Frame Relay, ATM, System Security.