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alt text I am using wireshark to analyse traffic that I captured with tcpdump but I am not sure if what I see is a DoS attack or port scanning. The file used can be downloaded from here

asked 21 Jul '14, 08:34

miky7's gravatar image

accept rate: 0%

edited 22 Jul '14, 04:16

Well, doing packet analysis based on a 'blackened' screenshot is nearly impossible! If you want an answer that is even close to the reality, you should post a capture file somewhere (google drive, dropbox, If you have any concerns regarding privacy issues, you can anonymize the file with TraceWrangler, a tool of our member @Jasper.

Now, based on the screenshot, I don't see any sign for a DDoS (distributed DoS), as there is only one IP address shown on the screenshot, which is not enough the talk about a distrubted DoS (DDoS).

Regarding a DoS: The screenshot hides the time stamps and there is no information at all what the IO graph is showing. So, it's impossible to tell if this is a DoS or a port scan.

However, based on my experience with DoS attacks, I'm almost sure that this is not a DoS attack, at least not an attack at the protocol level, as the IO graph would look different ;-)


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answered 22 Jul '14, 03:48

Kurt%20Knochner's gravatar image

Kurt Knochner ♦
accept rate: 15%

edited 22 Jul '14, 04:35

grahamb's gravatar image

grahamb ♦

Thank you for the reply. I will edit the post to include the file

(22 Jul '14, 04:11) miky7

O.K., with access to the capture file (updated question), this looks much more like an attack, even a bit like an attempt to run a DDoS.


  • There are different IP addresses, all trying the same. Not that much addresses, but still
  • They are not scanning different ports, they are 'hammering' all on the same ports (DNS, 445, 139, usw.). There is also mostly one target (, not a range of systems, so this is not a port scan.
  • They are sending the same DNS request again and again from different IP addresses (for:, which (sometimes) causes a server failure on your server

So, actually it looks like a DDoS, even though the frequency of the packets is not very high. However: sometimes it's enough to make your DNS server fail, for whatever reason (please check the logs).

To answer you question in the title:

How can I identify a DDoS/DoS attack with wireshark

I used the function

Statistics -> Conversations

and then I did some sorting in the TCP and UDP tabs. Then, with a bit of experience, you'll easily figure out if it's a port scan or an attempt to run a DDoS attack. See my explanations above.

(22 Jul '14, 09:00) Kurt Knochner ♦

Thank you very much for the reply! I also had the same impression but since it is the first time I saw a pcap capture, I was not sure. I also have some SYN flooding from a specific IP but the frequency is still quite low and the number of packets not that high. Perhaps an attempt to fool any IDS software?

(23 Jul '14, 03:16) miky7

Perhaps an attempt to fool any IDS software?


Or a test of a new tool. Or the preparation for the 'real' attack. Or kids playing with tools. Impossible to know ...

(23 Jul '14, 16:30) Kurt Knochner ♦
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question asked: 21 Jul '14, 08:34

question was seen: 56,888 times

last updated: 23 Jul '14, 16:30

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