Add to ORKGThis thesis is focused on design and implementation of tool for data extraction from captured network communication. The theoretical part deal with particular network protocols, its behavior, defines keywords and apprises with used tools. Second part is focused on design and implementation of extraction tool, design of declaration language for description of protocols. In the extractor are included third-party tools for analysis particular packets and reconstruction network flows. These tools together with designed declarative language are used due to requirement on easy extendability of designed tool. The end of this thesis is dedicated functional and performance testing of implemented tool