Posted: . At: 10:45 AM. This was 5 years ago. Post ID: 12992
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Sending longer strings as custom TCP packets is a lot of fun.

I have managed to send a longer string as a TCP packet with nping.

0000   d0 50 99 0d ab 0f 00 0c 29 6f 3b 80 08 00 45 00   ÐP..«...)o;...E.
0010   00 e3 07 90 00 00 40 06 ef 2b c0 a8 01 04 c0 a8   .ã....@.ï+À¨..À¨
0020   01 05 27 ff 01 bb 29 fa 38 90 00 00 00 00 50 02   ..'ÿ.»)ú8.....P.
0030   05 c8 0e 01 00 00 48 65 6c 6c 6f 20 57 6f 72 6c   .È....Hello Worl
0040   64 2e 20 54 68 69 73 20 69 73 20 61 20 63 75 73   d. This is a cus
0050   74 6f 6d 20 49 43 4d 50 20 70 61 63 6b 65 74 2e   tom SYN packet.
0060   20 49 20 6c 6f 76 65 20 73 65 6e 64 69 6e 67 20    I love sending 
0070   74 68 69 73 20 73 74 75 66 66 2e 20 59 6f 75 20   this stuff. You 
0080   63 61 6e 20 75 73 65 20 61 20 6c 6f 6e 67 20 73   can use a long s
0090   74 72 69 6e 67 20 61 73 20 77 65 6c 6c 2e 20 56   tring as well. V
00a0   65 72 79 20 6c 6f 6e 67 20 69 6e 64 65 65 64 2e   ery long indeed.
00b0   20 53 6f 20 6c 6f 6e 67 2c 20 69 74 20 62 6c 6f    So long, it blo
00c0   61 74 73 20 74 68 65 20 70 61 63 6b 65 74 20 71   ats the packet q
00d0   75 69 74 65 20 61 20 62 69 74 2c 20 62 75 74 20   uite a bit, but 
00e0   73 74 69 6c 6c 20 77 6f 72 6b 73 20 66 69 6e 65   still works fine
00f0   2e                                                .

Packet summary.

7147	288.878742	192.168.1.4	192.168.1.5	TCP	241	10239443 [SYN] Seq=0 Win=1480 Len=187

This was sent using nping, that comes with the nmap package on Linux. This allows sending custom TCP packets as a ping request to a remote machine, that may be captured with tcpdump or Wireshark. But if the packet is sent over SSH, it is encrypted and does not work well as a medium for sending a message. This could possibly be used to send a message, if the parts of the file were placed in the packets and then extracted and reassembled at the destination machine. Very interesting indeed.

This is the command I used to send this large network packet.

jason@hoshi:~$ sudo nping -c 1 --data-string "Hello World. This is a custom ICMP packet. I love sending this stuff. You can use a long string as well. Very long indeed. So long, it bloats the packet quite a bit, but still works fine." --tcp -p 80,443 192.168.1.2

This is a fun thing to try, it is up to you what you send as a message, even a small file would work.

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