1. Packet Analysis for Beginners Lisa Bock, Pennsylvania College of Technology

2. Topics Covered Overview of Packet Analysis The OSI Model The TCP/IP Protocol Suite  Normal Network Communication - TCP and UDP Abnormal Communication  Scanning  Malware

3. Overview of Packet Analysis Packet analysis uses a packet sniffer, network monitor or analyzer, to monitor and troubleshoot network traffic. As data flows across the network, the sniffer captures each packet decodes the packet's raw bits  Showing the field values in the packet according to the appropriate RFC or other specifications. The information can identify bottlenecks and help maintain efficient network data transmission.

4. Uses for Packet Analysis Analyze network problems Detect network intrusion attempts and network misuse Perform regulatory compliance through content monitoring perimeter and endpoint traffic Monitor bandwidth utilization Verify endpoint security status Gather and report network statistics

5. Some Common Packet Analyzers Cain and Abel Carnivore (FBI - monitors all of a target user's Internet traffic) dSniff ettercap ngrep, Network Grep OmniPeek Snoop Tcpdump Wireshark (formerly known as Ethereal)

6. Packet Capture Traffic captured is dependent on the placement of the device. On a switch, the packet sniffer will see only data going to and from the switch to the capture device Traffic seen will be unicast, broadcast, or multicast. To see all traffic, port monitoring or SPAN on a switch is used, or use a full duplex tap in line with traffic http://wiki.wireshark.org/CaptureSetup/Ethernet

7. The OSI Model In order to understand packet analysis you must understand the way data is prepared for transit. The OSI model, is a seven-layer representation of how data changes in form as each layer provides services to the next layer  Data encapsulates or de-encapsulates

8. The OSI Model MAC Port IP Address Data Frame Segment Packet PDU Bits

9. Wireshark The tool we will use for demonstration is Wireshark, formerly Ethereal, an open-source packet analyzer http://www.wireshark.orghttp://www.wireshark.org Download and install Wireshark – make sure you install WinPCap (Windows Packet Capture) if you are using Windows For a live capture, launch Wireshark and click the name of an interface under Capture Interfaces to start capturing packets on that interface.

10. Wireshark Configure advanced features by clicking Options Select the interface with active packet exchange Checkmark the interface you want to capture on

11. The OSI Model In Wireshark, select any TCP frame and you will see the frame contents from layer 2-7 Data Frame Segment Packet For a review go to http://wiki.wireshark.org/Ethernethttp://wiki.wireshark.org/Ethernet

12. Help in Wireshark Easily find help in Wireshark-including Sample Captures

13. Capture Packets We will be use pre-captured packets found in your folder and review they normal traffic versus abnormal traffic Once you open a capture you will see three panes:  The Packet List view - a list of all of the packets received during the capture session.  The middle window is the Details view.  The bottom is the individual Packet Bytes

14. TCP Example Normal traffic Three-way handshake packets 1,2,3 Review port numbers, flags, SEQ ACK numbers, stream index Packets 38-39 FIN packets Packet 4 get image: File->export objects http://www.symantec.com/connect/articles/studying-normal-traffic-part-three-tcp-headers

16. UDP Example Provides connectionless Transport Layer service to other applications on the internet without having to go through a handshake or connection process. It is a simple protocol and that does not provide any ordering or data integrity services. UDP is an unreliable service. Few problems occur with UDP.

17. What uses UDP? Commonly used in video streaming and time-sensitive applications. UDP Applications:  Domain Name System (DNS)  Routing Information Protocol (RIP)  Voice over IP (VoIP)  Trivial File Transfer Protocol (TFTP)  Domain Host Configuration Protocol (DHCP) 2015 Cengage Learning Computing Conference17

18. DNS Filter UDP and you will see the DNS packets Convert symbolic host names such (google.com) to an IP address (72.14.204.103) Transfers name information between DNS servers  DNS uses TCP in a zone transfer Look up other host names such as mail exchange (MX) records DNS is essential to any network

19. Normal DNS Queries/Responses Client sends query to DNS server for an IP address Server responds with information it has or asks other DNS servers for the information All DNS packets have four (4) sections:  Questions  Answer Resource Records  Authority Resources Records  Additional Resource Records

20. DNS Packet Structure - Flags If RD is set, it directs the name server to pursue the query recursively.

21. FTP – Grab a Pic Purpose of FTP is to transfer files over TCP Uses both ports 20 and 21  Command channel is designated on port 21 for the FTP server.  To transfer data like directory contents or files, a secondary channel, port 20 is used. Filter FTP-data traffic - then follow the TCP stream. Save as.jpg

22. Reassemble the Streams Can reassemble and obtain content if data is not encrypted Filter ftp-data traffic Right click follow TCP stream and save the file as raw data and click save as mystery.jpg Go to where you saved the file and open it!

23. Internet Control Message Protocol ICMP is used by routers, intermediary devices, or hosts to communicate updates or error information to other routers, intermediary devices, or hosts.  Used to troubleshoot network issues  Not used to exchange data between systems ICMP is used by ping because it can generate echo-request/echo-reply query messages. A Scout for IP!

24. Internet Control Message Protocol Four types of query messages that characterize the output generated by the ping command.  Echo request/echo reply:  Used to test reachability  Time stamp request/time stamp reply:  Used to compute delay between time stamps  Information request/information reply:  Locates address of local IP network  Subnet mask request/subnet mask reply:  Subnet information is exchange

25. ICMP-Dest Unreachable RFC 792 –” ICMP is actually an integral part of IP, and must be implemented by every IP module.”

26. ICMP Error Codes Type 3 Destination Unreachable Codes  0 - Net Unreachable  1 - Host Unreachable  2 - Protocol Unreachable Type 5 Redirect Codes  0 – Redirect Datagram for Network  1 – Redirect Datagram for Host  2 - Redirect Datagram for Type of Service

27. ICMP Error Codes Type 11 Time Exceeded Codes  0 – TTL Exceeded  1 – Fragment Reassembly Time Exceeded Type 12 Parameter Problem Codes  0 – Pointer Indicates the Error  1 – Missing Required Option  2 - Bad Length

28. ICMP - Errors Frame 5 Destination unreachable port unreachable snmp 161 A response with a nested packet  We have the IP header to send the packet to the target  After the destination unreachable message returns it sends back the IP header and 64 bits of original datagram ICMP is used in reconnaissance by Kali Linux http://it-ebooks.info/book/3000/

29. DDOS Go to http://map.ipviking.com/http://map.ipviking.com/ 2015 Cengage Learning Computing Conference29

30. Network Scans Nmap is a tool used to discover hosts and services on a network, and create a "map" of the network.  It can be either legitimately or maliciously used to quickly scan thousands of ports, and discrimination between ports in open, closed and filtered states. By default, Nmap performs a SYN Scan, which works against any TCP stack.

31. Nmap Scanning can be used as a passive attack in the form of reconnaissance. After running a scan, the software will output results from the IP range you selected:  PortslHosts - the results of the port scan, including the well-known services for those ports.  Topology - an interactive view of the connections between hosts in a network.  Host Details – Details such as the number of ports, IP addresses, hostnames, operating systems, and more.

32. Normal Three Way Handshake 2015 Cengage Learning Computing Conference32

33. Port Scan A command line tool such as tcpdump will provide a way to analyze traffic Open Wireshark OUT Do you see a pattern? An Ack Reset sent in response to a Syn frame is sent to acknowledge the receipt of the frame but then to let the client know that the server cannot allow the connection on that port. 2015 Cengage Learning Computing Conference33

34. Port Scan Same source and destination IP address Only the SYN flag is set The destination port numbers of each packet changes as it tries every port http://www.symantec.com/connect/articles/network-intrusion-detection-signatures- part-two

35. Port Scan Packets 14, 15 and 16 we see an actual connection Then it continues to attempt another connection in Packet 18, 19, 20 Enable SYN flood protection 2015 Cengage Learning Computing Conference35

36. SEC-Bittorrent BitTorrent uses a distributed sloppy hash table (DHT) for storing peer contact information for "trackerless" torrents and consists of a number of different queries and corresponding responses.  Ping G used to check if a peer is available.  Find_node G used to find the contact information for a peer.  Get_peers G requests a list of peers which have pieces of the content.  Announce_peer G announces the contact information for the peer to the network. Right click on packet 22 and follow UDP Stream

37. More Resources For more Packet Captures go to http://www.netresec.com/?page=PcapFiles http://www.netresec.com/?page=PcapFiles Wireshark Network Analysis, by Laura Chappell, Chappell Binding Paperback ISBN 978-1-893939-99-8 Practical Packet Analysis: Using Wireshark to Solve Real-World Network Problems, by Chris Sanders, No Starch Press, Incorporated ISBN-13: 9781593272661 2010