Rootkit In a Network Card Demonstrated

KindMind notes coverage in The Register on a researcher who has developed a firmware-based rootkit that resides in a network card. Here is the developer's blog entry. "Guillaume Delugré, a reverse engineer at French security firm Sogeti ESEC, was able to develop proof-of-concept code after studying the firmware from Broadcom Ethernet NetExtreme PCI Ethernet cards... Using the knowledge gained from this process, Delugré was able to develop custom firmware code and flash the device so that his proof-of-concept code ran on the CPU of the network card."

Old News

[chrisG23]

But still completely and utterly fascinating and relevant, especially since no one seemed to pay to much attention back at CANSECWEST (yet another computer security/tool/hacker/exploit research convention) this year in March when the same group shared their research and did a live demonstration of getting root (or system level, I forget if they hacked a windows or linux box) over the network by taking over the NIC, and not doing anything at all through the host OS.

See their writeup here www.ssi.gouv.fr/IMG/pdf/csw-trustnetworkcard.pdf or go to their company's website http://www.ssi.gouv.fr/site_article185.html [ssi.gouv.fr]

Re:how do you hide it?

[h4rr4r]

By doing what they do now, pull one out of every X and take a look at it.

Sensationalized

[tom229]

"However, the attack presented only applies to a specific network card model (Broadcom NetXtreme) whenever a remote administration functionality (called ASF for Alert Standard Format 2.0) is turned on (it is off by default) and configured. According to vendors, this functionality is far from being widely used. As a consequence, this vulnerability is really likely to have a very limited impact in practice."

Doesnt seem like theres much to worry about.

Re:I wonder about the next gen of attacks...

[cachimaster]

I'm sure people are familar with LoJack for Laptops, where either due to a hook in BIOS (Dells and HPs have an option that will reinstall the LoJack software even if the BIOS is reflashed and all disks are zapped) or other means it gets loaded.

It's not a hook, LoJack comes with every BIOS. That's why it survives reflashing, you don't have the option of a BIOS without it. I co-wrote some article [coresecurity.com] about this not long ago.

How to fix? The obvious fix would be signing the flash BIOS, but this completely locks out homebrewers wanting to do something different. Another fix would be having the flash process be offline, such as only though a USB port with a usb flash drive. However, NICs won't have USB ports present. Still another possible avenue would be a slot for a MicroSD card, but that adds complexity to the device. So, this isn't something easy to deal with. The only thing that might come close would be a DIP switch toggle to allow for unsigned images to be flashed (which is shipped off), and all updates signed.

None of this would work. Maybe it will make it more difficult, but can't protect you against a logical flaw in the firmware that allows you to execute code. Firmware is like any other software, what happens if you sign code that executes any code? then all code is automatically "signed".

The solution IMHO is complex, expensive and involves signing+software protections in the NIC and in the OS (I.E. iommu, etc.) and WILL fail with a sufficiently resourceful attacker.

BTW, awesome work.

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