January 12, 2017
After Part 1 which focused on setting up your network for IoT this post focus on making sure that the devices are the right ones and that they work in your network. The first can be accomplished by asking basic security questions and talking only with the more secure vendors further. In my experience that also leads to the better vendors which know IT and whom will make your life easier in the long run. There are plenty of vendors out there for whom the whole IT part is new as they are an old vendor in a given field which now needs to do the “network thing” and don’t have the employees for it. Johannes B. Ullrich at SANS ISC InfoSec came up with the idea to preselect IoT vendors with 5 questions. (You can read more on his reasoning behind each question in his post):
5 preselect questions
- For how long, after I purchase a device, should I expect security updates?
This time frame will show us how long we can plan to use the device in our network, as using devices which get no security updates will be a compliance violation in most companies.
- How will I learn about security updates?
Responsible vendors will add you to a security mailing list where you will get informed on all security related stuff via email.
- Can you share a pentest report for your device?
If the vendor cares at all at security he let an external expert make a pentest, which will at least find the worst and stupid security holes. If the vendor is able to show you such an report, you should really take that vendor in consideration.
- How can I report vulnerabilities?
We often found security holes in programs or devices and sometimes it is really hard to report that to the vendor in a way he accepts it and fixes the hole in a reasonable time frame. Sometimes we needed to go via our local Austrian CERT and sometimes that even was not enough as the vendor was in the US and only did something after their CERT asked them pointed questions. So a direct connection the guy(s) responsible for the security of device is important.
- If you use encryption, then disclose what algorithms you use and how it is implemented
If the vendor tells you something about “Proprietary” run away from the product! If you read that they use MD5 or RC4, the software on the device seems a little bit dated.
After selecting the best vendors ranked by the preselect questions you should make sure that the devices will run in your network. If you’re new to this kind of work you will not believe what garbage some vendors deliver. Some points are connected to your network and how it will look in the future.
- The device needs to support DHCP!
- Use DHCP reservations to provide fixed IP addresses
- Special case in a secure network is to disable ARP learning on the Layer 3 switches (makes MitM attack a lot harder). In this case DHCP is used for filling the ARP table.
- Check if the device will work with MAC oder 802.1x authentication flawlessly
- Some devices only send a packet if queried, which won’t work if the device got de-authenticated e.g. idle timeout or network problem. The device needs to send a packet ever so often so the switch sees the MAC address and can make a RADIUS request.
- The devices needs to support routing
- We had devices that where only able to talk within the subnet. In some cases we were not sure if the product really didn’t support it or just the technician was unable to configure it.
- As the PCs and servers need to be separated via a Firewall (see Part 1), this feature is a deal breaker
- It should be possible to configure a local NTP Server
- If not, the device time runs off or you need to allow the device to connect to the Internet, which can get complicated or insecure if you’ve different devices each using an other NTP server
- The devices needs to support automatic restart of services after power or network outage
- We had some devices which needed manual interventions to reconnect to the servers again after a network problem
- Embedding of external resources should be looked at. e.g. If a device needs jquery for its web GUI and lets the browser load that via jquery.org it will not work it your Internet is down. In some cases that does not matter, in some thats a deal breaker.
- support of 1Gbit Ethernet connection
- Sure I know that IoT devices do not need 1Gibt, but the devices will maybe run 10 years and you’ll have 10Gbit switches by than. It is not sure that 100Mbit will be supported or work flawlessly. e.g. Some current Broadcom 10Gbit chipsets don’t support 100Mbit half duplex anymore. You need an other chipset which is a little bit more expensive .. and you know what switch vendors will pick? 😉
So so far for part 2 of this series … the next part will be on some policy stuff you need to agree with department wanting that devices.