n Understand EC-Council s scanning methodology n Describe scan types and the objectives of scanning

Transcription

1 Outline n Understand EC-Council s scanning methodology n Describe scan types and the objectives of scanning n Understand the use of various scanning and enumeration tools Chapter #3: n Describe TCP communication (three-way handshake and flag types) n Understand basic subnetting n Understand enumeration and enumeration techniques n Describe vulnerability scanning concepts and actions n Describe the steps involved in performing enumeration 2 Phases of Hacking Scanning n Scanning is the process of discovering systems on the network and taking a look at what open ports and applications may be running n Footprinting general network information about its makeup n Scanning goes into the network and start touching each device to find out more about them 3 4 1

2 n Recipient system gets a frame n Layer 3 address is verified in the packet header and the header is stripped off n it checks the physical address n if the address is indeed correct, it opens the frame, checks to n The remaining PDU (Protocol Data Unit), now called a make sure the frame is valid segment, is passed to Layer 4 n then ditches the header and trailer, passing the remainder up to the Network layer 5 6 Connectionless Communication n At the Transport layer, a whole host of important stuff n At the Transport layer, connectionless communication is happens end-to-end delivery, segment order, reliability, accomplished with UDP and flow control are all Layer 4 functions including TCP n It is a low-overhead, simple, and fast transport protocol flags and port numbering n Generally application protocols that use this transport method are moving small amounts of data n Examples of protocols using UDP are TFTP, DNS (for lookups), and DHCP 7 8 2

3 Connectionless Communication n TCP is a lot slower than connectionless but a much more orderly form of data exchange n Sender will establish connection before data transfer n Flow control during communication n Three-way handshake

4 TCP Header Flags Ports n SYN (Synchronize) This flag is set during initial communication establishment It indicates negotiation of parameters and sequence n Inside the Transport-layer protocol header (TCP or UDP) a numbers port number identifies which upper-layer protocol should n ACK (Acknowledgment) This flag is set as an acknowledgment to SYN receive the information flags This flag is set on all segments after the initial SYN flag n RST (Reset) This flag forces a termination of communications (in both directions) n FIN (Finish) This flag signifies an ordered close to communications n PSH (Push) This flag forces the delivery of data without concern for any buffering In other words, the receiving device need not wait for the buffer to fill up before processing the data n URG (Urgent) When this flag is set, it indicates the data inside is being sent out of band Cancelling a message mid-stream is one example Ports Active Ports n Well-known ports n Registered ports ,151 n Dynamic ports 49,152 65,

5 netstat n netstat a vs netstat -an There is no 100 percent secure system, n netstat at vs netstat au n netstat lt vs netstat lu vs netstat lx and there is nothing that is foolproof! n netstat s vs netstat st vs netstat -su Stay Alert! 17 5