In this paper a vulnerability penetration testing for several hosts in WLAN is made. The exploited operating systems were Microsoft Windows 7Enterprise and Microsoft Windows 8. It has been used an exploit named “Java storeImageArray () Invalid Array Index-ing Vulnerability”. Thanks to the open source penetration testing platform - Metasploit Framework the exploit was executed on the target hosts. The most important and critical rea-son the attack being successfully executed is connected with the human factor and interven-tion. Thereby, some security professionals and network administrators can use Metasploit Framework neither to run exploit nor to write security scripts in order to detect and protect the computer and network resources against various malicious cyber-attacks.

In this paper a small corporate building with four working computer departments using dynamic routing protocol - RIP is designed and made. Dynamic routes are the most important step in the construction of any computer network. Subnetting is one of the best network tools with that each system and network administrator is able to divide one specific computer network into many subnetworks. Thereby, some network administrators, security professionals and network architects can use the free of charge software program Cisco Packet Tracer in order to design and administer different corporate computer networks.

In this paper a common detectionand implementation of Alternate Data Streams in the operating system Windows Server 2008 R2 is made. Nowadays it is very important each system administrator and security professional to detect and analyze different types of alternate data streams. These steams can hide sensible secret or malicious files that can damage some of the computer and networks resources.

In this paper a performance and connection analysis of determined computer systems and networks is made. Each communication process and state must be daily scanned and analyzed by system administrators, security-professionals and IT specialists. Ensuring a secure flow of computer and network processes and performance is very important priority for many large and small companies and for normal users. Most of the malicious user and programmers use vulnerability in the selected network via determined computer and network processes.

Essential component of organizing stage of the counteraction for the en-croachment against the business organization is to identify vulnerabilities of the social organization. The purpose of this stage is to identify all existing and potential weaknesses and disadvantages of the security system of the organization, creating a circumstance for adversely effects on the sources of threat.