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Cisco IOS Hack's Part 1.

HOWTO modify some Text Mesages from the IOS

And here some important Info's
for testing purpose only!
maybe it's aganist your local law!
it can damage your device!
and read the copyright iinfos from cisco, and remember, in some countrys it's not allowed, to reverse engeneer Software.

For this Test, i use my dynamips/dynagen enviroment For more datailed infos about Dynampis and dynagen see following links
DYNAMIPS
DYNAGEN

Preparing the IOS

Unpacking the IOS
The IOS images are normaly compressed, and for using with a hexeditor, you must uncompress the image.
For uncompressing use unzip from linux or cygwin. If you recive a error message, ignore it. ;-)

	unzip c3745-adventerprisek9-mz.123-14.T7.bin

Find the Text Strings

Start Up your Router with the "original" IOS

	Trying 127.0.0.1...
	Connected to localhost.
	Escape character is '^]'.
	Connected to Dynamips VM "R1" (ID 0, type c3745) - Console port
	
	              Restricted Rights Legend
	
	Use, duplication, or disclosure by the Government is
	subject to restrictions as set forth in subparagraph
	(c) of the Commercial Computer Software - Restricted
	Rights clause at FAR sec. 52.227-19 and subparagraph
	(c) (1) (ii) of the Rights in Technical Data and Computer
	Software clause at DFARS sec. 252.227-7013.

And here you find some Keywords like Restricted Rights Legend
and now, you can edit your uncompressed image with a hexeditor
Open the IOS image and serach for the Stings, you have seen on the normal startup

Now, you can change the Text with your new Text. But its important, that you replace the same count of chars, that are there before. Finaly, you must have the size of text, then before!

With Dynamips you can now direct use the uncompressd and modified image.
And here you see a smale change in the Boot messages ;-)

And now, you can replace some other Text Messages.
and remember, never edit the orginal image, use a copy of the ios-image.