need help with wireshark

Hi Experts,

I have to make a scan for Fortinet.
Now I have seen millions of broadcast queries on the network.
Most of them directly from one machine.
Can you help me to read and understand the content of it ?
Why this source MAC makes so many ARP requests ?
See the PIC.
Broadcast-Storm.JPG
Eprs_AdminSystem ArchitectAsked:
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Fred MarshallConnect With a Mentor PrincipalCommented:
You install HITMANPRO on a computer and there is a little running man icon at the bottom of the window (at least I think that's the control you need).  Anyway there's a utility in the program to write a boot version onto a USB Flash Drive.  It's very nicely packaged that way.

Then, when you boot the computer just make sure that a USB Flash Drive is possible to boot from.  Usually there's a boot menu that will allow you to select without changing BIOS settings.  HITMANPRO gives you 3 choices for the mode it works in.  #1 is "best", #2 is, well, #2 and #3 is the last resort.  In some or all of these cases it looks like Windows is booting thereafter but don't be alarmed.  When it starts to get going, HITMANPRO starts up.
I've seen quite a few where #1 didn't work and still got good results.
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Dave HoweSoftware and Hardware EngineerCommented:
Usually? it isn't. The usual cause of a broadcast storm is a routing loop at layer 2 - i.e. switches hooked into each other so that there is more than one path between two routers, so broadcast traffic goes around and around...

many switches detect and block that (aka "spanning tree"), except when there is a vmware vswitch between them (which can route the traffic but blocks the packets loop detection detects)

check your architecture to see if you have a routing loop.
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Eprs_AdminSystem ArchitectAuthor Commented:
ok, we found out, because we check the MAC addresses.
And two machines are causing this broadcast storm.
When we disconnect one machine, the broadcast storm ends.

What can it be on the machine ?
It is laptop.
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giltjrCommented:
You need to see what type of packets it is sending.

The one sample you gave was a ARP.  The host that sent it was trying to find out the MAC address for a IP host.  Sending ARP's is normal and ARPs are broadcasts.

Does his machine talk to a lot of hosts?

Does his machine do any type of network scanning?

Does his machine constantly send out ARP's or does it send out a bunch and then do nothing for awhile, then send out a bunch more?
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Eprs_AdminSystem ArchitectAuthor Commented:
This machine sends out permanent ARP request.
This machines tries to ask each subnet, also subnets which are not configured and used.
No network scanner is installed or used.
what else can it be ?
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giltjrCommented:
A virus/worm.
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Eprs_AdminSystem ArchitectAuthor Commented:
we have scanned with 3 differnet anti virus and rootkit scanner.
There is noting on it.

Why this nic is sending so many arp requests ?
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Dave HoweSoftware and Hardware EngineerCommented:
try running Microsoft Network Monitor and/or ProcMon
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giltjrCommented:
What operating system is the laptop running?
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Eprs_AdminSystem ArchitectAuthor Commented:
The OS is WIN7
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Fred MarshallPrincipalCommented:
we have scanned with 3 different anti virus and rootkit scanner.
OK
There is noting on it.
Really, this conclusion should be:
None of the ones we used found anything.

I suggest you try some others.  I have cleaned machines where the 6th scanner found what was needed to be found.  At the same time, the first 5 were well-respected tools that I use most often.  NONE of them are perfect.
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giltjrCommented:
If you did not, I would also use something that you have to boot from CD or thumb drive.  Running a scanner under Windows, even in "safe" mode, does not always work.

Is there any other suspicious traffic other than the ARP's coming from his computer?  I would assume anything (virus or valid tool) that is sending out ARP's would want to use the results of those ARP's to do or look for something else.
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Eprs_AdminSystem ArchitectAuthor Commented:
thanks
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Fred MarshallConnect With a Mentor PrincipalCommented:
HitManPro is a pretty good tool that can boot from a USB flash drive.  It's made to get things before they can start.
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giltjrConnect With a Mentor Commented:
I have used both:

Kaspersky Rescue Disk
F-Secure Rescue CD

If you have wired Internet access most of these will download the latest pattern files to scan with.
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Eprs_AdminSystem ArchitectAuthor Commented:
I know HITMANPRO but not the boot version.
Where can I find it ?
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