How can I read pcap files in a friendly format?

Question

a simple cat on the pcap file looks terrible:

$cat tcp_dump.pcap

?ò????YVJ?
          JJ
            ?@@.?E<??@@
?CA??qe?U????иh?
.Ceh?YVJ??
          JJ
            ?@@.?E<??@@
CA??qe?U????еz?
.ChV?YVJ$?JJ
            ?@@.?E<-/@@A?CAͼ?9????F???A&?
.Ck??YVJgeJJ@@.?Ӣ#3E<@3{nͼ?9CA??P?ɝ?F???<K?
?ԛ`.Ck??YVJgeBB
               ?@@.?E4-0@@AFCAͼ?9????F?P?ʀ???
.Ck??ԛ`?YVJ?""@@.?Ӣ#3E?L@3?Iͼ?9CA??P?ʝ?F?????
?ԛ?.Ck?220-rly-da03.mx

etc.

I tried to make it prettier with:

sudo tcpdump -ttttnnr tcp_dump.pcap
reading from file tcp_dump.pcap, link-type EN10MB (Ethernet)
2009-07-09 20:57:40.819734 IP 67.23.28.65.49237 > 216.239.113.101.25: S 2535121895:2535121895(0) win 5840 <mss 1460,sackOK,timestamp 776168808 0,nop,wscale 5>
2009-07-09 20:57:43.819905 IP 67.23.28.65.49237 > 216.239.113.101.25: S 2535121895:2535121895(0) win 5840 <mss 1460,sackOK,timestamp 776169558 0,nop,wscale 5>
2009-07-09 20:57:47.248100 IP 67.23.28.65.42385 > 205.188.159.57.25: S 2644526720:2644526720(0) win 5840 <mss 1460,sackOK,timestamp 776170415 0,nop,wscale 5>
2009-07-09 20:57:47.288103 IP 205.188.159.57.25 > 67.23.28.65.42385: S 1358829769:1358829769(0) ack 2644526721 win 5792 <mss 1460,sackOK,timestamp 4292123488 776170415,nop,wscale 2>
2009-07-09 20:57:47.288103 IP 67.23.28.65.42385 > 205.188.159.57.25: . ack 1 win 183 <nop,nop,timestamp 776170425 4292123488>
2009-07-09 20:57:47.368107 IP 205.188.159.57.25 > 67.23.28.65.42385: P 1:481(480) ack 1 win 1448 <nop,nop,timestamp 4292123568 776170425>
2009-07-09 20:57:47.368107 IP 67.23.28.65.42385 > 205.188.159.57.25: . ack 481 win 216 <nop,nop,timestamp 776170445 4292123568>
2009-07-09 20:57:47.368107 IP 67.23.28.65.42385 > 205.188.159.57.25: P 1:18(17) ack 481 win 216 <nop,nop,timestamp 776170445 4292123568>
2009-07-09 20:57:47.404109 IP 205.188.159.57.25 > 67.23.28.65.42385: . ack 18 win 1448 <nop,nop,timestamp 4292123606 776170445>
2009-07-09 20:57:47.404109 IP 205.188.159.57.25 > 67.23.28.65.42385: P 481:536(55) ack 18 win 1448 <nop,nop,timestamp 4292123606 776170445>
2009-07-09 20:57:47.404109 IP 67.23.28.65.42385 > 205.188.159.57.25: P 18:44(26) ack 536 win 216 <nop,nop,timestamp 776170454 4292123606>
2009-07-09 20:57:47.444112 IP 205.188.159.57.25 > 67.23.28.65.42385: P 536:581(45) ack 44 win 1448 <nop,nop,timestamp 4292123644 776170454>
2009-07-09 20:57:47.484114 IP 67.23.28.65.42385 > 205.188.159.57.25: . ack 581 win 216 <nop,nop,timestamp 776170474 4292123644>
2009-07-09 20:57:47.616121 IP 67.23.28.65.42385 > 205.188.159.57.25: P 44:50(6) ack 581 win 216 <nop,nop,timestamp 776170507 4292123644>
2009-07-09 20:57:47.652123 IP 205.188.159.57.25 > 67.23.28.65.42385: P 581:589(8) ack 50 win 1448 <nop,nop,timestamp 4292123855 776170507>
2009-07-09 20:57:47.652123 IP 67.23.28.65.42385 > 205.188.159.57.25: . ack 589 win 216 <nop,nop,timestamp 776170516 4292123855>
2009-07-09 20:57:47.652123 IP 67.23.28.65.42385 > 205.188.159.57.25: P 50:56(6) ack 589 win 216 <nop,nop,timestamp 776170516 4292123855>
2009-07-09 20:57:47.652123 IP 67.23.28.65.42385 > 205.188.159.57.25: F 56:56(0) ack 589 win 216 <nop,nop,timestamp 776170516 4292123855>
2009-07-09 20:57:47.668124 IP 67.23.28.65.49239 > 216.239.113.101.25: S 2642380481:2642380481(0) win 5840 <mss 1460,sackOK,timestamp 776170520 0,nop,wscale 5>
2009-07-09 20:57:47.692126 IP 205.188.159.57.25 > 67.23.28.65.42385: P 589:618(29) ack 57 win 1448 <nop,nop,timestamp 4292123893 776170516>
2009-07-09 20:57:47.692126 IP 67.23.28.65.42385 > 205.188.159.57.25: R 2644526777:2644526777(0) win 0
2009-07-09 20:57:47.692126 IP 205.188.159.57.25 > 67.23.28.65.42385: F 618:618(0) ack 57 win 1448 <nop,nop,timestamp 4292123893 776170516>
2009-07-09 20:57:47.692126 IP 67.23.28.65.42385 > 205.188.159.57.25: R 2644526777:2644526777(0) win 0

Well...that is much prettier but it doesn't show the actual messages. I can actually extract more information just viewing the RAW file. What is the best ( and preferably easiest) way to just view all the contents of the pcap file?

UPDATE

Thanks to the responses below, I made some progress. Here is what it looks like now:

tcpdump -qns 0 -A -r blah.pcap
    20:57:47.368107 IP 205.188.159.57.25 > 67.23.28.65.42385: tcp 480
        0x0000:  4500 0214 834c 4000 3306 f649 cdbc 9f39  E....L@.3..I...9
        0x0010:  4317 1c41 0019 a591 50fe 18ca 9da0 4681  C..A....P.....F.
        0x0020:  8018 05a8 848f 0000 0101 080a ffd4 9bb0  ................
        0x0030:  2e43 6bb9 3232 302d 726c 792d 6461 3033  .Ck.220-rly-da03
        0x0040:  2e6d 782e 616f 6c2e 636f 6d20 4553 4d54  .mx.aol.com.ESMT
        0x0050:  5020 6d61 696c 5f72 656c 6179 5f69 6e2d  P.mail_relay_in-
        0x0060:  6461 3033 2e34 3b20 5468 752c 2030 3920  da03.4;.Thu,.09.
        0x0070:  4a75 6c20 3230 3039 2031 363a 3537 3a34  Jul.2009.16:57:4
        0x0080:  3720 2d30 3430 300d 0a32 3230 2d41 6d65  7.-0400..220-Ame
        0x0090:  7269 6361 204f 6e6c 696e 6520 2841 4f4c  rica.Online.(AOL
        0x00a0:  2920 616e 6420 6974 7320 6166 6669 6c69  ).and.its.affili
        0x00b0:  6174 6564 2063 6f6d 7061 6e69 6573 2064  ated.companies.d

etc.

This looks good, but it still makes the actual message on the right difficult to read. Is there a way to view those messages in a more friendly way?

UPDATE

This made it pretty:

tcpick -C -yP -r tcp_dump.pcap

Thanks!

I was able to extract a readable email from pcap data using 'strings' — Yaakov Kuperman, Sep 17 '13 at 22:35

score 157 · Accepted Answer · answered Jul 09 '09 at 21:32

157

Wireshark is probably the best, but if you want/need to look at the payload without loading up a GUI you can use the -X or -A options

tcpdump -qns 0 -X -r serverfault_request.pcap

14:28:33.800865 IP 10.2.4.243.41997 > 69.59.196.212.80: tcp 1097
        0x0000:  4500 047d b9c4 4000 4006 63b2 0a02 04f3  E..}..@.@.c.....
        0x0010:  453b c4d4 a40d 0050 f0d4 4747 f847 3ad5  E;.....P..GG.G:.
        0x0020:  8018 f8e0 1d74 0000 0101 080a 0425 4e6d  .....t.......%Nm
        0x0030:  0382 68a1 4745 5420 2f71 7565 7374 696f  ..h.GET./questio
        0x0040:  6e73 2048 5454 502f 312e 310d 0a48 6f73  ns.HTTP/1.1..Hos
        0x0050:  743a 2073 6572 7665 7266 6175 6c74 2e63  t:.serverfault.c
        0x0060:  6f6d 0d0a 5573 6572 2d41 6765 6e74 3a20  om..User-Agent:.
        0x0070:  4d6f 7a69 6c6c 612f 352e 3020 2858 3131  Mozilla/5.0.(X11
        0x0080:  3b20 553b 204c 696e 7578 2069 3638 363b  ;.U;.Linux.i686;

tcpdump -qns 0 -A -r serverfault_request.pcap

14:29:33.256929 IP 10.2.4.243.41997 > 69.59.196.212.80: tcp 1097
E..}..@.@.c.
...E;...^M.P..^w.G.......t.....
.%.}..l.GET /questions HTTP/1.1
Host: serverfault.com

There are many other tools for reading and getting stats, extracting payloads and so on. A quick look on the number of things that depend on libpcap in the debian package repository gives a list of 50+ tools that can be used to slice, dice, view, and manipulate captures in various ways.

For example.

answered Jul 09 '09 at 21:32

Zoredache

128,755
40
271
413

5

Upvoted. It can make for messy reading, but useful for those in-the-field scenarios. Which reminds me - ngrep! – Dan Carley Jul 09 '09 at 21:52
the tcpdump commands you gave are better but i am still not really getting what i want. i updated my question to reflect that. the wireshark installation didn't work and i don't want to install it unless i have to. thanks for your help so far and let me know if you have any other suggestions. – Tony Jul 09 '09 at 23:12
4

ok, this command seemed to do it with tcpick. it would probably benefit others it you added it to your answer "tcpick -C -yP -r tcp_dump.pcap" – Tony Jul 09 '09 at 23:20
2

providercorga - you could add it to your answer instead of someone else going to the effort, and you might get points too. just sayin'. – Jul 10 '09 at 11:00
ok, il do that. just wanted to try and give Zoredache credit since he gave a great answer – Tony Aug 03 '09 at 22:08
I am getting permission denied when I try this command, even if I use sudo. Any ideas how I can solve this? – Goaler444 May 01 '13 at 11:51
`tcpdump -qns 0 -A -r file.pcap` is rlly useful in CTFs :smirk: – John D Oct 01 '18 at 07:42

score 33 · Answer 2 · answered Jul 09 '09 at 21:21

33

Wireshark.

You may never look back :)

Incidentally you should make sure the snaplen of your original capture matches or exceeds the MTU of the traffic that you're capturing. Otherwise the contents will appear truncated.

answered Jul 09 '09 at 21:21

Dan Carley

25,189
5
52
70

Also you may want to use -w to do a binary dump and -s 200 to lengthen the packet snapshot (if you are looking at name server or nfs packets). – Adam Brand Jul 09 '09 at 21:32
Wireshark is great - but not ideal when working with limit resources on a VM. – User Oct 16 '17 at 01:54

score 29 · Answer 3 · edited Jan 13 '12 at 09:21

29

tshark -r file.pcap -V is very useful if you're stuck without wireshark/gui.

edited Jan 13 '12 at 09:21

quanta

50,327
19
152
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answered Jul 27 '09 at 17:49

Marcin

2,281
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score 25 · Answer 4 · answered Jul 09 '09 at 21:37

You can use wireshark which is a gui app or you can use tshark which is it's cli counterpart.

Besides, you can visualize the pcap using several visualization tools:

tnv - The Network Visualizer or Time-based Network Visualizer
afterglow - A collection of scripts which facilitate the process of generating graphs
INAV - Interactive Network Active-traffic Visualization

If you want to analyze the pcap file you can use the excelent nsm-console.

Last, but not least, you can upload your pcap to pcapr.net and watch it there. pcapr.net is a kind of social website to analyze and comment to traffic captures.

score 4 · Answer 5 · answered Jul 09 '09 at 21:21

4

You can simply load pcap files in Wireshark to browse them.

answered Jul 09 '09 at 21:21

Emmanuel BERNAT

312
1
6

score 2 · Answer 6 · answered Nov 26 '12 at 10:59

2

You can directly view/capture the remote packets to wireshark using tcpdump.

Remote packet capture using WireShark & tcpdump

How to Use tcpdump to capture in a pcap file (wireshark dump)

answered Nov 26 '12 at 10:59

Rahul Panwar

23
3

How can I read pcap files in a friendly format?

6 Answers6

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