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Drinking from the network hose

So What is WireShark?

• Packet sniffer/protocol analyzer• Open Source Network Tool• Latest version of the ethereal tool

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Source: www.fcc.gov

A packet is a “chunk” of data l d ienclosed in a wrapper

• What’s a network?• What’s an IP address?• What’s a MAC address?

Stuff we won’t cover

• What’s a router?• What do you mean capture?• Can this make Elite run faster?• What’s open source?• How can one man look so bald?

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Ok…why would I want to use it?• Analyze network problems (worms, viruses, malware, etc.)• Detect network intrusion attempts• Monitor network usage• Gather and report network statistics• Filter suspect content for management review• Spy on network users• Reverse engineer protocols and network applications• Debug client/server communicationsebug c e t/se e co u cat o s• Find chatty devices (like printers)• Find hacked computers on your network• Look for “heavy” users of the Internet• Find “missing” computers and devices• Determine network loads (after baselining of course)• Find misconfigured computers and devices• Identify non-used protocols that are turned on by accident• Learn more about how networks work• Identify application dependencies• Impress your friends with your inner geekdom

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libpcaplibpcap

Installation on Windows

• wireshark-setup.exe /S /desktopicon=yes /quicklaunchicon=no

N t B i i l d i t ll d ifNote: Be sure winpcap is already installed if you install by command line. During a GUI install, you have the option to install winpcap.

Help File• Version 1.0 of WireShark was recently

released. It is distributed with an older Helpfile (24665 ver 0.099.7). To get the latest help file, download it fromlatest help file, download it from www.wireshark.org separately.

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Installation on Linux

• CENTOS – yum install wireshark• Ubuntu – apt-get install wireshark• Red Hat – rpm –iv wireshark*rpm

• In most cases dependencies (like libpcap) are installed automatically…because Linux installers rock

tsharkC:\Program Files\Wireshark>tshark -helpTShark 1.0.0Dump and analyze network traffic.See http://www.wireshark.org for more information.

Copyright 1998-2008 Gerald Combs <gerald@wireshark.org> and contributors.This is free software; see the source for copying conditions. There is NOwarranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Usage: tshark [options] ...

Capture interface:-i <interface> name or idx of interface (def: first non-loopback)-f <capture filter> packet filter in libpcap filter syntax-s <snaplen> packet snapshot length (def: 65535)-p don't capture in promiscuous mode-B <buffer size> size of kernel buffer (def: 1MB)-y <link type> link layer type (def: first appropriate)-D print list of interfaces and exit-L print list of link-layer types of iface and exit

Capture stop conditions:-c <packet count> stop after n packets (def: infinite)-a <autostop cond.> ... duration:NUM - stop after NUM seconds

filesize:NUM - stop this file after NUM KBfiles:NUM - stop after NUM files

………..

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With traffic…

Summary Window

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Decode Window

HEX Window

Menu Bar

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Button Bar

Status Bar

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Status Bar

Location, Location, Location

Hub

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Hubs

• If you’re capturing on a hub you should see all traffic passing on layer 2 network

D l S d h b b d• Dual Speed hub = badThere are lots of issues with these due to internal caching of data. Stay away from them, or at least check the WireShark Wiki for ones that are known to work.

Switches• Switches isolate traffic• On a switch you will only see broadcast

traffic and traffic destined for the existing PCPC

• SPAN or Mirroring ports “copy” traffic from another port or group of ports

Switch with a SPAN port

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TAP

Which is better?

A h b TAP SPAN t?A hub, TAP or a SPAN port?

It dependsIt depends…

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HUBS

Switch

interface FastEthernet0/1port monitor FastEthernet0/2

VLAN Monitoring

interface FastEthernet0/1port monitor VLAN1

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Types of TAPs

• Copper & Optical• Conversion TAPs• Aggregator TAPs• Full-Duplex TAPs• Hub – Technically…a hub is a half duplex

TAP, but you may miss critical layer 1 events

Why to use a TAP• Physical layer errors aren’t seen by SPAN• SPAN increase the CPU on your switch• Timestamps are more accurate when using a

TAP• SPAN ports hide jitter (loss of synchronicity)• After 50% port utilization you begin to drop

packets (if you monitor both transmit & receive) – sometimes you can fix this

• They are non-intrusive• It makes you look really cool

ARP Cache Poisoning

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My rules of thumb

If you are concerned about a specific device, use a TAP.

If you want to see more then one device traffic use a SPAN port.

If it’s a busy line, use a TAP or you risk drops

Setting promiscuous mode

Simple Capture

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Capture Interfaces

Capture Options

Capture Filters (Pre-Filters)

• Capture filters (sometimes called pre-filters or ingress filters) watch all incoming traffic for specific patterns or characteristics Only data matching thecharacteristics. Only data matching the filter gets through

• The format is based on tcpdump filter language

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Capture Filter exampleshost 10.1.11.24This filter will capture all data where the ip address 10.1.11.24 appears in the packet source or

destination field.

host 192.168.0.1 and host 10.1.11.1This filter will capture all ip data between host 192.18.0.1 and 10.1.11.1.

tcp port httpThis filter will capture all http, (TCP port 80) traffic.

ipThis filer will capture all IP traffic, regardless of IP address.

not broadcast not multicastUh….hum….everything but broadcasts and multicasts ;)

ether host 00:04:13:00:09:a3All traffic from and to the MAC address defined above

Capture Filter

Capture Options

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Capture Interfaces

Interface Details: Characteristics

Interface Details: Statistics

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Interface Details: 802.3 (Ethernet)

Interface Details: Task Offload

Checksum

A checksum is a form of redundancy check, a simple way to protect the integrity of data by detecting errors in data that are sent through

space or time. It works by adding up the basic components of a message, typically the assorted bits, and storing the resulting value.

Anyone can later perform the same operation on the data, compare the result to the authentic checksum, and (assuming that the sums match)

conclude that the message was most likely not corrupted.

Source: Wikipedia.com

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Checksum offload

This can cause false positive i t k d Ifissues on some network cards. If

you see tons of incorrect checksum messages…turn off checksum

offload.

Turning off Checksum offloadOn Linux (as root)ethtool -K eth0 rx off tx off (choose correct network interface if not eth0)

On FreeBSD (as root):ifconfig em0 -rcxsum -tcxsum (choose correct network interface if not em0)

On MacOS (as root):sysctl -w net.link.ether.inet.apple_hwcksum_tx=0sysctl -w net.link.ether.inet.apple_hwcksum_rx=0

Turning off Checksum offload

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Stopping the Packet Capture

Filters

Display Filters (Post-Filters)

• Display filters (also called post-filters) only filter the view of what you are seeing. All packets in the capture still exist in the tracetrace

• Display filters use their own format and are much more powerful then capture filters

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Display Filter

Display Filter Examplesip.src==10.1.11.24 all ip traffic with the source address of 10.1.11.24

ip.addr==192.168.1.10 && ip.addr==192.168.1.20 Traffic which is between IP 192.168.1.10 and 192.168.1.20.

tcp.port==80 || tcp.port==3389 Traffic from any machine but it will only be TCP Port 80 (HTTP) or TCP Port 3389 (RDP)

!(ip.addr==192.168.1.10 && ip.addr==192.168.1.20) Traffic except the traffic between these two machines.

(ip.addr==192.168.1.10 && ip.addr==192.168.1.20) && tcp.port==445 || tcp.port==139 SMB traffic between these two machines.

(ip.addr==192.168.1.10 && ip.addr==192.168.1.20) && (udp.port==67 || udp.port==68) DHCP Traffic between these two machines

Protocol Hierarchy

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Protocol Hierarchy

Follow TCP Stream

Follow TCP Streamred - stuff you sent blue - stuff you get

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Expert Info

Expert Info

Conversations

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Conversations

IOGraphs

IOGraphs

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IOGraphs

IOGraphs

IOGraphs

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Flow Graphs

Flow Graphs

Flow Graphs

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Right Click Filtering

Right Click FilteringPrepare loads the Display filter box, but doesn’t apply it

Apply load they filter AND applies it

Export HTTP

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Export HTTP Objects

Triggered Stops

Triggered Stops

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Service Response Time - SMB

Service Response Time - SMB

Service Response Time - SMB

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VOIP

VOIP Calls

VOIP Call Graph

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VOIP RTP Player

SIP Analysis

SIP Analysis

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HTTP Analysis

HTTP Analysis – Load Distribution

HTTP Analysis – Packet Counter

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HTTP Analysis – Requests

TroubleShooting TCP

• Latency• Loss• Jitter• Jabber• Small Packets

Latency

The time it takes for a packet to travel from point a to point b

L t i ft thLatency is often the cause of “slow” networks

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Troubleshooting TCP Latency

T1

T1 is the time it took from the moment the syn was sent until the client received the syn/ack

This time is due to the wire latency + processing time of the IP stack on the server

T2

T2 is the time it took from receiving the SYN/ACK until the ACK is sent.

This time is the processing time of the IP stack on the client

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T3

T3 is the time it took from sending the ACK until the clients sends a GET.

This time is the processing time of the application on the client

T4

T4 is the time it took from sending GET until an ACK is received at the client.

This time is due to wire latency.

T5

T5 is the time it took from getting the ACK until data is received at the client.

This time is due the server application.

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TIPS• Time #1 & #4 should be small on a LAN application. If not, check

your network path, nic settings and throughput.• Time #2 is the client ip stack. Should be minimal. If not, check the

driver.• Time #3 is the client application. This time will undoubtedly vary

greatly between packets Talk to your developers if you see andgreatly between packets. Talk to your developers if you see and issue here.

• Time #5 is the server application. This time will also vary greatly, but generally if #5 is huge and #4 is really, really small look at delays caused by the server application. Start troubleshooting on the server by looking at CPU, bandwidth, memory and disk IO.

Jitter

Jitter is an unwanted variation of one or more characteristics of a periodic signal in electronics and telecommunications. Jitter may be seen in characteristics such as themay be seen in characteristics such as the interval between successive pulses, or the amplitude, frequency, or phase of successive cycles.

Source: Wikipedia.com

Jitter

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Jitter

Jitter

Jitter

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LOSS

Um…lost packets ☺

Source: me

LOSS

Jabber

• Jabber occurs when there are excessively long packets from a network device.

• This isn’t very common on IP only networks but is very common onnetworks, but is very common on multiprotocol networks

• Simply check for packet size

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Packet Size

Packet Length

Improving WireShark Performance

• Don’t use capture filters• Increase your read buffer size• Don’t update the screen dynamically• Get a faster computer• Use a TAP• Don’t resolve names

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Thank you