reverse engineering modem firmware

[AnarchyAngel]

So im trying to modify the firmware of a ddr2200 modem and add a few programs like netcat and so on.


image used - http://home.centurytel.net/ihd/ciscoddr2200/Cisco%20DDR-2200%203.40.5E%20DHCP%20Firmware%20for%20IPTV%20&%20HSI%20over%20ADSL2+%20Bonding.bin


I used binwalk and brfwmod to split the bin into rootfs.bin, kernl.bin, and tag.bin
i then used lzma_unsquash to decompress rootfs.bin and edit the file system, then I zipped it back up but i have no idea how to pack it with the kernl and tag bins to something the modem can use. ideas?

[p1c4rus]

Hi.

You need infect kern.bin file (parse opcodes and find empty or modifiable blocks and point to jump your code  etc...). If you like build new rom you need code for compile this. I don't remember well but if you firmware use hash for detect changes in kernel.

The Moon is a malware with infection firmwares purposes.

Regards.