Introduction to Packet Sniffing using Ethereal 0.10.9
-
Upload
alfreda-golden -
Category
Documents
-
view
101 -
download
0
description
Transcript of Introduction to Packet Sniffing using Ethereal 0.10.9
Introduction to Packet Sniffingusing Ethereal 0.10.9
Rob Bergin
Network Engineer
The Timberland Company
Non-Technical
Currently Data just travels around your network like a train. With a packet sniffer, get the ability to capture the data and look inside the packets to see what is actually moving long the tracks.
Technical
Ethereal (and WinPcap)
Ethereal – Application for Sniffing Packets
WinPcap – open source library for packet capture
Operating System – Windows & Unix/Linux
NPF device driver Network Driver(WinPcap runs as a protocol driver like TCP.SYS)
Network Card Drivers
WinPcap Architecture
Frame 1
WinPcap is an open source library for packet capture and network analysis for the Win32 platforms. It includes a kernel-level packet filter, a low-level dynamic link library (packet.dll), and a high-level and system-independent library (wpcap.dll, based on libpcap version 0.6.2).
The packet filter is a device driver that adds to Windows 95, 98, ME, NT, 2000, XP and 2003 the ability to capture and send raw data from a network card, with the possibility to filter and store in a buffer the captured packets.
Packet.dll is an API that can be used to directly access the functions of the packet driver, offering a programming interface independent from the Microsoft OS.
Wpcap.dll exports a set of high level capture primitives that are compatible with libpcap, the well known Unix capture library. These functions allow to capture packets in a way independent from the underlying network hardware and operating system.
WinPcap is released under a BSD-style license.
Ethereal Application
• Requires WinPcap for Captures • Can run standalone to examine captures
A Capture
Frame 1 Frame 2 Frame 3 Frame 4 Frame 5 Frame 6
• Let’s define a capture as a period of time that Ethereal captured data frames.
• Frames can be assembled to examine application traffic
Recap
• Packet Sniffing
• Ethereal
• Data Frame Architecture
• WinPcap
• Network Capture
Basic TCP/IP Stuff
Interoperable TCP/IP
• TCP/IP is Transmission Control Protocol/Internet Protocol) is a suite of network protocols.
• TCP and IP are two separate protocols
• TCP handles the data (HTTP vs. FTP vs. Telnet)
• IP handles the data transmission (i.e. between routers).
• TCP/IP protocols were designed to allow different applications running on dissimilar operating systems to communicate across a network.
Watch your Headers
TCP / UDP- Ports not Addresses- Layer 4 not 3- FTP uses 20 and 21
IP- Addresses not Ports- Layer 3 not 4- 192.168.1.1 (octet)
TCP
• TCP is connection-oriented transport layer protocol designed to provide a reliable connection for data exchange between two systems.
• TCP ensures that all packets are properly sequenced and acknowledged and that a connection is established before data is sent.
• TCP provides it reliability through the use of an acknowledgement or ACK.
TCP
• If a receiving system had to send an ACK for every packet, the result would be an incredible amount of overhead for the network.
• To reduce the overhead, a mechanism called windowing is used.
• Windowing is a method of flow control.
TCP
• The receiving system advertises a certain number of packets that it can receive at a time (input buffer size.)
• The sending system watches for an ACK after the designated number of packets is sent.
• If an ACK is not received, data will be retransmitted from the point of the last ACK.
UDP
• UDP (User Datagram Protocol) provides an unreliable, connectionless protocol to deliver packets.
• This protocol allows messages, called datagrams, to be sent without the overhead of ACKs, established connections, and sequencing.
• Applications that use UDP as their communications mechanism include NFS (2049), TFTP (79), DNS (53) and Unreal Tournament (7777).
IPv4
• IP (Internet Protocol) is used to handle datagram services between hosts.
• IP handles the addressing, routing, and reassembly
• IP addresses are 32 bits long, are organized into 4 octets (8 bits) separated by periods
• IPv4 address examples: 192.168.10.20.
• IPv6 is a next generation form of addressing.
IPv6
• IP (Internet Protocol) is used to handle datagram services between hosts.
• IP handles the addressing, routing, and reassembly
• IP addresses are 32 bits long, are organized into 4 octets (8 bits) separated by periods
• IPv4 address examples: 192.168.10.20.
• IPv6 is a next generation form of addressing.
What will IPv6 look like?IPv6 Addresses:CDFE:910A:2356:5709:8475:1024:3911:2021
2080:0000:0000:0000:0090:7AEB:1000:123A
Combo IPv4 and IPv61800:0000:0000:7AEF:0000:0000:16.114.67.16
Compacted IPv6 Address:2080:0:0:0:90:7AEB:1000:123A Legal compaction2080::90:7AEB:1000:123A Legal compaction1800::7AEF:0:0:1072:4310 Legal compaction
IPv4 vs. IPv6
• IPv4 RFC came out in 1981.
• IPv6 RFC came out in 1998.
0
200
400
600
800
1000
1200
1400
1600
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Millions
Mobile Subscriber
s
PCs Connectedto Web
MobileInternet
Users
Sources: ABN AMRO/IDC/Ovum
Recap
• TCP vs. IP
• Headers
• TCP
• UDP
• IP
• IPv4 vs. IPv6
Ethereal Overview
View of Ethereal
Packet List
Packet Details
Packet Bytes
Packet List Packet Order
Time Order
Source IP
Destination IP
Protocol
Information
Packet Details
Breakdown of the Frame, the Packet, the TCP portion
Source and Destination IP
Source and Destination TCP Ports
Packet Bytes
View of the data – Hexidecimal and Raw Data
Ethereal Capture
Running Ethereal
Ethereal Analysis
Logging on to FTP Server
What Ethereal saw
What Ethereal saw
What Ethereal saw
What Ethereal saw
What Ethereal saw
Ethereal Filtering.
Filtering!!!!
Saving Captures
• Captured Views• Range of Packets• All Packets• Naming is critical:
– Was it the client?– Was it the Server?
After Filter/Save/Open
Time Column & Delta
FTP Only Filter
Ethereal Packet Analysis
What Username?
Is Password Required?
What Password?
Why can’t I log in?
Follow the Stream
Advanced Filtering
Filter for just that stream
(ip.addr eq 207.46.133.140 and ip.addr eq 172.17.22.56) and (tcp.port eq 21 and tcp.port eq 3511)
Filter for traffic between two hosts
ip.addr == 207.46.133.140 and ip.addr == 172.17.22.56
Filter for IP Traffic and removal of other traffic
ip and !(nbns) and !(msnms) and !(browser) and !(rip)
Summary Info
Ethereal: Encryption
HTTP
HTTPS
HTTP vs. HTTPS
HTTP vs. HTTPS
HTTP vs. HTTPS
TCP Stream vs. HTML Source
Ethereal: Miscellaneous
Protocol Hierarchy
I/O Graphing
HTTP Breakdown
Coloring Packets
Commercial Sniffers
• Sniffer Pro
• OmniPeek
• Observer
• IT Guru and ACE
Final Words
“If you can’t measure it, you can’t manage it”
- Peter Drucker