chaosreader [-aehikqrvxAHIRTUXY] [-D dir]
            [-b port[,...]] [-B port[,...]]
            [-j IPaddr[,...]] [-J IPaddr[,...]]
            [-l port[,...]] [-L port[,...]] [-m bytes[k]]
            [-M bytes[k]] [-o "time"|"size"|"type"|"ip"]
            [-p port[,...]] [-P port[,...]]
            infile [infile2 ...]

chaosreader -s [mins] | -S [mins[,count]]
            [-z] [-f 'filter']


Chaosreader traces TCP/UDP/others sessions and fetches application data from snoop or tcpdump logs. This is a type of "any-snarf" program, as it will fetch telnet sessions, FTP files, HTTP transfers (HTML, GIF, JPEG etc) and SMTP emails from the captured data inside network traffic logs. A html index file is created to that links to all the session details, including realtime replay programs for telnet, rlogin, IRC, X11 and VNC sessions. Chaosreader reports such as image reports and HTTP GET/POST content reports.

Chaosreader can also run in standalone mode, where it invokes tcpdump to create the log files and then processes them.


-a, --application Create application session files (default)

-e, --everything Create HTML 2-way & hex files for everything

-h Print a brief help

--help Print verbose help (this) and version

--help2 Print massive help

-i, --info Create info file

-q, --quiet Quiet, no output to screen

-r, --raw Create raw files

-v, --verbose Verbose - Create ALL files .. (except -e)

-x, --index Create index files (default)

-A, --noapplication Exclude application session files

-H, --hex Include hex dumps (slow)

-I, --noinfo Exclude info files

-R, --noraw Exclude raw files

-T, --notcp Exclude TCP traffic

-U, --noudp Exclude UDP traffic

-Y, --noicmp Exclude ICMP traffic

-X, --noindex Exclude index files

-k, --keydata Create extra files for keystroke analysis

-D dir, --dir dir Output all files to this directory

-b 25,79, --playtcp 25,79 replay these TCP ports as well (playback)

-B 36,42, --playudp 36,42 replay these UDP ports as well (playback)

-l 7,79, --htmltcp 7,79 Create HTML for these TCP ports as well

-L 7,123, --htmludp 7,123 Create HTML for these UDP ports as well

-m 1k, --min 1k Min size of connection to save ("k" for Kb)

-M 1024k, --max 1k Max size of connection to save ("k" for Kb)

-o size, --sort size sort Order: time/size/type/ip (Default time)

-p 21,23, --port 21,23 Only examine these ports (TCP & UDP)

-P 80,81, --noport 80,81 Exclude these ports (TCP & UDP)

-s 5, --runonce 5 Standalone. Run tcpdump/snoop for 5 mins.

-S 5,10, --runmany 5,10 Standalone, many. 10 samples of 5 mins each.

-S 5, --runmany 5 Standalone, endless. 5 min samples forever.

-z, --runredo Standalone, redo. Rereads last run's logs.

-j, --ipaddr Only examine these IPs

-J, --noipaddr Exclude these IPs

-f 'port 7', --filter 'port 7' With standalone, use this dump filter.


index.html Html index (full details)

index.text Text index

index.file File index for standalone redo mode

image.html HTML report of images

getpost.html HTML report of HTTP GET/POST requests Info file describing TCP session #1

session_0001.telnet.html HTML coloured 2-way capture (time sorted)

session_0001.telnet.raw Raw data 2-way capture (time sorted)

session_0001.telnet.raw1 Raw 1-way capture (assembeled) server->client

session_0001.telnet.raw2 Raw 1-way capture (assembeled) client->server

session_0002.web.html HTML coloured 2-way

session_0002.part_01.html HTTP portion of the above, a HTML file

session_0003.web.html HTML coloured 2-way

session_0003.part_01.jpeg HTTP portion of the above, a JPEG file

session_0004.web.html HTML coloured 2-way

session_0004.part_01.gif HTTP portion of the above, a GIF file

session_0005.part_01.ftp-data.gz An FTP transfer, a gz file.


session_* TCP Sessions

stream_* UDP Streams

icmp_* ICMP packets

index.html HTML Index

index.text Text Index

index.file File Index for standalone redo mode only

image.html HTML report of images

getpost.html HTML report of HTTP GET/POST requests

*.info Info file describing the Session/Stream

*.raw Raw data 2-way capture (time sorted)

*.raw1 Raw 1-way capture (assembeled) server->client

*.raw2 Raw 1-way capture (assembeled) client->server

*.replay Session replay program (perl)

*.partial.* Partial capture (tcpdump/snoop were aware of drops)

*.hex.html 2-way Hex dump, rendered in coloured HTML

*.hex.text 2-way Hex dump in plain text

*.X11.replay X11 replay script (talks X11)

*.textX11.replay X11 communicated text replay script (text only)

*.textX11.html 2-way text report, rendered in red/blue HTML

*.keydata Keystroke delay data file. Used for SSH analysis.


Normal eg "chaosreader infile", this is where a tcpdump/snoop file was created previously and chaosreader reads and processes it.

Standalone once eg "chaosreader -s 10" this is where chaosreader runs tcpdump/snoop and generates the log file, in this case for 10 i minutes, and then processes the result. Some OS's may not have tcpdump or snoop available so this will not work (instead you may be able to get Ethereal, run it, save to a file, then use normal mode). There is a master index.html and the report index.html in a sub dir, which is of the format out_YYYYMMDD-hhmm, eg "out_20031003-2221".

Standalone, many eg "chaosreader -S 5,12", this is where chaosreader runs tcpdump/snoop and generates many log files, in this case it samples 12 times for 5 minutes each. While this is running, the master index.html can be viewed to watch progress, which links to minor index.html reports in each sub directory.

Standalone, redo eg "chaosreader -ve -z", (the -z), this is where a standalone capture was previously performed - and now you would like to reprocess the logs - perhaps with different options (in this case, "-ve"). It reads index.file to determine which capture logs to read.

Standalone, endless eg "chaosreader -S 5", like standalone many - but runs forever (if you ever had the need?). Watch your disk space!

Note: this is a work in progress, some of the code is a little unpolished.


  • Run chaosreader in an empty directory.

  • Create small packet dumps. Chaosreader uses around 5x the dump size in memory. A 100Mb file could need 500Mb of RAM to process.

  • Your tcpdump may allow "-s0" (entire packet) instead of "-s9000".

  • Beware of using too much disk space, especially standalone mode.

  • If you capture too many small connections giving a huge index.html, try using the -m option to ignore small connections. eg "-m 1k".

  • snoop logs may actually work better. Snoop logs are based on RFC1761, however there are many varients of tcpdump/libpcap and this program cannot read them all. If you have Ethereal you can create snoop logs during the "save as" option. On Solaris use "snoop -o logfile".

  • tcpdump logs may not be portable between OSs that use different sized timestamps or endian.

  • Logs are best created in a memory filesystem for speed, usually /tmp.

  • For X11 or VNC playbacks, first practise by replaying a recent captured session of your own. The biggest problem is colour depth, your screen must match the capture. For X11 check authentication (xhost +), for VNC check the viewers options (-8bit, "Hextile", ...)

  • SSH analysis can be performed with the "sshkeydata" program as demonstrated on . chaosreader provides the input files (*.keydata) that sshkeydata analyses.


  • The following assumptions may cause problems (check for new vers);

  • A lower port number = the service type. Eg with ports 31247 and 23, the actual type of session is telnet (23). This may not work for some things (eg, VNC).

  • Time based order is more important for 2-way sessions (eg telnet), SEQ order is more import for 1-way transfers (eg ftp-data).

  • One particular TCP session isn't active for long enough that the SEQ number loops (or even wraps).


  • Example 1:

      tcpdump -s9000 -w out1; chaosreader out1; netscape index.html


snoop -o out1; chaosreader out1; netscape index.html


ethereal (save as "out1"); chaosreader out1; netscape index.html


chaosreader -s 5; netscape index.html

  • Example 2:

      tcpdump -s9000 -w output1        # create tcpdump capture file

      chaosreader output1              # extract recognised sessions, or,

      chaosreader -ve output1          # gimme everything, or,

      chaosreader -p 20,21,23 output1  # only ftp and telnet...

  • Example 3:

      snoop -o output1                 # create snoop capture file instead

      chaosreader output1              # extract recognised sessions...

  • Example 4:

      chaosreader -S 2,5      # Standalone, sniff network 5 times for 2 mins
                              # each. View index.html for progress (or .text)

RELATED TO chaosreader…

tcpdump(8), chaosreader help page.


chaosreader was written by Brendan Gregg.

This manual page was written by Joao Eriberto Mota Filho <[email protected]> for the Debian project (but may be used by others). The base of this text was caught off chaosreader source code.