Create a dummy files using dd

Let's explore creating files using the unix dd feature. Unix dd utility is a diskduplicator and you can create  bogus files that later you can use ethically or unethically within certain packet forge scenarios

For example, if you wanted to create a file & with that data,  appended to maybe hping ( -E ) or with sendip ( -f)  as a payload.  So let's say I want a random data in a file 1meg big. We could easily craft this using cmds

dynamic-90:~ kfelix$ dd  if=/dev/random of=./myfile.file bs=1024 count=1000
1000+0 records in
1000+0 records out
1024000 bytes transferred in 0.076096 secs (13456676 bytes/sec)
dynamic-90:~ kfelix$ sh
sh-3.2$ dd  if=/dev/random of=./myfile.file bs=1024 count=1000
1000+0 records in
1000+0 records out
1024000 bytes transferred in 0.073255 secs (13978602 bytes/sec)
sh-3.2$ 

and a quick listing of the file shows

-rw-r--r--  1 kfelix  1523313980  1024000 Dec 13 17:16 myfile.file

You can confirm the contents using the unix od or hexdump cmd;

e.g
sh-3.2$ od myfile.file

sh-3.2$ hexdump myfile.file

the Data should be randomize

Now let's do the same but using  a file padded with zeros

sh-3.2$
sh-3.2$ dd  if=/dev/zero of=./myfile.file bs=1024 count=1000
1000+0 records in
1000+0 records out
1024000 bytes transferred in 0.005179 secs (197724302 bytes/sec)
sh-3.2$
sh-3.2$
sh-3.2$ ls -l myfile.file
-rw-r--r--  1 kfelix  1523313980  1024000 Dec 13 17:20 myfile.file
sh-3.2$

Okay and od and hexdump will show us the contents;

sh-3.2$ od myfile.file
0000000    000000  000000  000000  000000  000000  000000  000000  000000
*
3720000
sh-3.2$ 

sh-3.2$ hexdump myfile.file
0000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
*
00fa000
sh-3.2$

sh-3.2$ hexdump myfile.file 



i hope this was helpful, happy packet forging

Ken Felix
Freelance Network Security Engineer
kfelix  a-t hyperfeed dot com