Randomize your WiFi MAC address on Ubuntu

https://www.paulfurley.com/randomize-your-wifi-mac-address-on-ubuntu-1604-xenial/

by paulfurley • 9 years ago

211 105 9 years ago

pedrocr3• 9 years ago

This seems like it should be a default indeed. It does make it harder to assign fixed addresses to your devices in your home network. At least openwrt only seems to have static DHCP leases based on MAC and not on the advertised DHCP name. For most devices this doesn't matter as it does add a DNS entry with whatever IP it assigned. But when you then want to add a firewall rule to port forward something to a device a fixed IP is much nicer.

paulfurley17• 9 years ago

True - I could update the script to allow for whitelisting certain networks so they receive a stable-forever MAC address..?

pedrocr3• 9 years ago

That would probably make a lot of sense. Can the network manager setting also be changed per network? It would be nice to do this with the normal config in the future.

evilDagmar2• 9 years ago

What makes it easier is having fixed goals in mind, because I am seeing a lot of people in this thread arguing because they're all solving different problems which is obviously going to mean different solutions.

If your only concern is passive tracking, then a randomized MAC being used for SSID probes (because whitelist-only hidden SSIDs are rare enough that those people can manually connect) will be sufficient.

If you're looking to keep an open Wifi provider from tracking you over the course of days, then using a different MAC for each connect is going to be sufficient.

If you're looking to avoid tracking by people doing traffic analysis to correlate by behaviour no amount of MAC trickery will help you.

If one is looking to avoid having to pay for overstaying their visit at a coffee house or similar capture portal, maybe what needs to be changed is one's sense of ethics, and changing a MAC won't help with that.

So, you can say "it should be a default" all you like, but everyone's going to have a different idea of what the default is for and they're going to throw a fit about it not being "the right default". Better to be conservative like Android and avoid inciting the newbs.

pedrocr3• 9 years ago

Your different problems with different solutions have at least a part that everyone agrees on like iOS doing it for probes. We can definitely argue what the right default is but will probably agree that no randomization at all is not a good one and move to at least some. Ubuntu currently does none.

jimmaswell2• 9 years ago

This would be a bad default because it breaks things like staying signed into a network with a login gateway.

dbolgheroni• 9 years ago

In OpenBSD, it's just:

  # ifconfig iwn0 lladdr random

Of course, iwn0 is your interface.

paulfurley17• 9 years ago

There's probably a one-liner in Linux too, but not one which satisfies the three caveats in the post.

microcolonel3• 9 years ago

The necessary infrastructure exists in wpa_supplicant, but only in a newer version than is distributed with Ubuntu 16.04. OpenBSD is more integrated, so advanced functionality like this tends to be easily accessed through ifconfig.

diggan• 9 years ago

I've used https://github.com/feross/SpoofMAC in the past, which is a simple python tool for doing just this, cross-platform. Used it a lot in airports and can warmly recommend using it if you're usually dealing with multiple different OSes and don't want to remember how to do it for each.

gingerlime• 9 years ago

Looks cool. I wish there was something like this for iPhone/iPad - which is much more likely to be with me everywhere and leak my MAC...

side note/question: do I need to actively connect to a WIFI network for them to know my MAC or does it leak even when my phone scans for neighbouring SSIDs? EDIT: looks like MAC would leak even if I don't connect to any access point, but my Wifi is on... At least according to [0]

EDIT 2: looks like iPhone and Android use MAC randomization when scanning WIFI. (not sure after they connect though). But even this randomization can be defeated[1]?

[0] https://www.crc.id.au/tracking-people-via-wifi-even-when-not... [1] https://www.theregister.co.uk/2017/03/10/mac_address_randomi...

sml156• 9 years ago

I am pretty sure that when iPhone connects to an access point it uses the real mac, I don't know about android but it is probably the same.

Some access points need your real mac to connect because they use that to authorize you, I think schools/universities use this method a lot.

paulfurley17• 9 years ago

Good tip, thanks for linking to this.

mobilemidget• 9 years ago

Are there any lawyers here that can speak about the legal side of this? I could imagine a wifi provider that offers 30 minutes free wifi e.g. airports, has this covered in their terms and conditions or a country that could consider this as fraudulent?

izacus• 9 years ago

iPhones and Android phones do this for awhile already. If you read the article you'll notice that the MAC stays the same for a SSID for a working day. This makes sure it doesn't break networking and as a side effect captcha portal limits still work.

paulfurley17• 9 years ago

I believe iPhones and Android phones only do it while in scanning mode. Once connected, they use the real MAC address.

propogandist• 9 years ago

FYI re:

iPhone - "Researchers Break MAC Address Randomization and Track 100% of Test Devices"

https://www.bleepingcomputer.com/news/security/researchers-b...

Android - "Only an estimated 6% of Android phones randomize MACs, and they do it poorly."

https://arstechnica.com/information-technology/2017/03/shiel...

bgaluszka• 9 years ago

Here https://blogs.gnome.org/thaller/2016/08/26/mac-address-spoof... is how you can do it with newer NetworkManager.

paulfurley17• 9 years ago

If anyone here's involved developing NetworkManager, it would be brilliant to see a 'stable-for-n-days' type setting. This would prevent a WiFi network tracking you over time, as well as between networks.

conradk• 9 years ago

I've found GNU macchanger to be the easiest way to do that kind of stuff. It's as simple as:

macchanger -r <interface>

Interesting article about macchanger on the Arch Wiki: https://wiki.archlinux.org/index.php/MAC_address_spoofing

paulfurley17• 9 years ago

I also used macchanger in the past but it seems that recent versions of NetworkManager overwrite the changes that macchanger makes.

jandrese2• 9 years ago

Another case where NetworkManager pissed me off. A couple of years ago they broke all third party MAC changers in favor of their built-in solution, but the built-in solution required the bleeding edge head version of wpa_supplicant that no vendor shipped leaving the entire system nonfunctional. IIRC it still doesn't work on Ubuntu 16.

larrykwg• 9 years ago

This seems like a good idea until you realize that you are the only one using a random mac address. (There is a vendor prefix at the beginning of every mac) Better would be to take a bit more care in choosing a more realistic address.

paulfurley17• 9 years ago

Yep, feel free to modify to spoof a real hardware MAC address (as the original version of my blog post suggested: https://github.com/paulfurley/www.paulfurley.com/commit/bebc...)

As @_fink on Twitter pointed out, colliding with a real existing MAC address is not ideal.

throwmenow_01408• 9 years ago

I think it's not a good idea to change your mac address as your only precaution against tracking. The DNS requests you'll make will reveal which sites you frequent.

I would advise to use a VPN connection. In this case it doesn't matter that you've randomized your mac address in a way which can be clearly identified as random. And even then you can see the VPN server IP in the logs so you should also make precautions and buy your VPN connection anonymously (and even then - you'll never know if you're really anonymous).

Changing your mac address seems to be sufficient (in addition to the VPN usage) to prevent easy tracking through something unique like your real mac address. But I agree that this is just 1-3 lines of code for realistic mac address generation so it should be unproblematic to add.

Edit: If you have fears of being uncovered by random-looking mac addresses without vendor prefixes, changing your mac address will probably not help you. Your threat model is different - maybe APT-level - and you have to do way more than changing your mac address.

Tharkun• 9 years ago

If you're paranoid enough to be spoofing your MAC address, surely you're paranoid enough not to rely on shady DNS servers?

tinus_hn3• 9 years ago

Your adversary probably isn’t the NSA, it’s commercial tracking services. Their business is tracking the general public, they don’t care about one weird person.

Unless avoiding this becomes common practice and then the whole story changes.

throwmenow_01408• 9 years ago

Here is the code I use for my mac to randomize my mac address:

    interface="en0"
    new_mac=$(openssl rand -hex 6 | sed 's/\(..\)/\1:/g; s/:$//; s/./0/2') # from stackoverflow
    sudo ifconfig $interface ether $new_mac

Edit: What's the advantage of the solution in the post? If I just change my mac address every time I join a network (even the same one), they can't track me with my randomized mac addresses. So why would I prefer to keep a stable but randomized mac address for each network I connect to for a day?

xigency• 9 years ago

Because maybe you had to pay to access the network and part of that involved binding your mac address.

For example, calling the hotel desk to get your device to work.

throwmenow_01408• 9 years ago

Would be interested where that happens because I've never encountered something like this (binding the mac to the access) in public networks e.g. McDonald's, hotels and other shops. I did only get access codes which could be used for a specific time where I just changed my mac address.

I only know about mac whitelisting in protected networks managed by wary administrators.

jlgaddis• 9 years ago

Some bits of the MAC address are significant. You're generating all 48 bits randomly which could have some side effects.

throwmenow_01408• 9 years ago

Would love to know which side effects there are. I've never encountered any problems in all those years I use those randomly generated mac addresses.

rurban2• 9 years ago

    new_mac=$(openssl rand -hex 4 | sed 's/\(..\)/\1:/g; s/:$//; s/./0/2'; s/^/02:/)

is better. by using the 02: prefix for locally administered macs you avoid clashes with certain cards. I also used to randomize my local hostname.

throwmenow_01408• 9 years ago

Most of the time there are <100 devices connected to the wifis I'm connected to. I don't want to do the math now, but I expect that a collision is pretty unlikely. If you mean that some cards have problems with handling those mac addresses, I would love to hear about that.

I also used to randomize my local hostname

Great idea, missed that. I'll integrate that in the future.

microcolonel3• 9 years ago

On systemd-networkd, you can add

    [Link]
    MACAddressPolicy=random

and (for RFC 7844[13] DHCP Anonymity Profiles)

    [DHCP]
    Anonymize=true

to your network unit or link.

microcolonel3• 9 years ago

MAC address randomization is in fact built in to NetworkManager (edit: 1.4), so none of this work is really necessary (edit: if you are on 1.4 or later).

NetworkManager also includes more advanced modes which make the MAC address stable for a given hotspot, but random between them.

https://blogs.gnome.org/thaller/2016/08/26/mac-address-spoof...

paulfurley17• 9 years ago

Unless you're using Ubuntu 16.04 LTS, in which case you're stuck with NetworkManager 1.2.

From the post: "I learned that NetworkManager 1.4.1+ can do MAC address randomization right out the box. If you’re using Ubuntu 17.04 upwards, you can get most of the way with this config file."

PascLeRasc• 9 years ago

Will these new randomized MACs also be lookupable [1] to find the model? If I'm the feds running honeypot wifi and I see a different Dell Chromebook doing things interesting to me every day, this isn't a good cover.

[1] https://www.macvendorlookup.com/

tscs37• 9 years ago

Not necessarily. However, if you're the only random MAC user on a network, it can be trackable.

Depending on implementation the MAC will have a specific bit set to indicate it is user supplied and not necessarily universally unique but I'm not sure if NM does that.

paulfurley17• 9 years ago

No, because they use the 'locally administered' prefix [1]. This is deliberate in order not to collide with real existing MAC addresses. (The original version of the post used real, Intel MAC prefixes [2] and you can look in the gist revision for that code if you prefer.)

BTW if it's really the feds you're worried about, this article probably isn't for you.

[1] https://en.wikipedia.org/wiki/MAC_address#Universal_vs._loca...

[2] https://github.com/paulfurley/www.paulfurley.com/commit/bebc...

kawsper• 9 years ago

NSA MAC address prefix is 00:20:91, you can combine this knowledge with the one from the article to scare your sysadmins.

paulfurley17• 9 years ago

Amazing!!

dreamcompiler• 9 years ago

This threw me for a minute. The NSA is not what I would consider an ethernet vendor. But it's true: https://news.ycombinator.com/item?id=11792320

emmelaich2• 9 years ago

There's probably a lot more fun ones. Complete list at http://standards-oui.ieee.org/oui.txt. 3.6Mb.

    $ grep 00-20-91 oui.txt 
    00-20-91   (hex)		J125, NATIONAL SECURITY AGENCY
    $ egrep -ic 'army|force|navy|secur|secret|private' oui.txt 
    461

andrewshadura4• 9 years ago

Unfortunately, this isn't compatible with a bunch of popular wireless cards, mostly from Realtek.

paulfurley17• 9 years ago

Damn, I didn't know about these. Do you know what it is that makes them incompatible? And is there a list of cards you can avoid?

andrewshadura4• 9 years ago

Here: https://bugzilla.gnome.org/show_bug.cgi?id=777523

andrewshadura4• 9 years ago

Also, some Broadcoms in Linux before 4.9.

Theodores• 9 years ago

Realtek and Ubuntu - I have spent four years trying to get my wifi to work. Being tracked would be a bonus, the built in wifi on my Lenovo laptop is deaf to the world and will never get as far as MAC spoofing.

andrewshadura4• 9 years ago

There's a work-around in the comment above.

You're welcome to contribute to https://bugs.debian.org/849077 and https://bugs.debian.org/849875.

buildbuildbuild• 9 years ago

Be aware that this technique could be illegal or appear suspicious in some jurisdictions. MAC address randomization was mentioned in Aaron Swartz's indictment for wire fraud.

See page 7: https://www.wired.com/images_blogs/threatlevel/2012/09/swart...

lowglow3• 9 years ago

Can you show me where changing your MAC address is illegal?

ashleyn• 9 years ago

It's not illegal, it can be detected and then used against you in an indictment. It's like saying you dislike someone, they go missing, and the prosecutor mentions what you said.

CJefferson• 9 years ago

The law cares about intent.

Changing your Mac address, or wearing a fake beard, are both fine.

Changing your Mac address to trick a Wi-Fi hotspot which gives out one hour free per device per day, or using a fake beard to trick a shop keeper into letting you get "one free bagel per person" twice, is a crime.

just1nn2• 9 years ago

Where would MAC address capture occur on the network? MACs are local to L2 traffic, so once a frame turns into a packet and is routed, the sMAC of your PC is no longer present in the data. If you're on your home network, this has no impact what so ever.

paulfurley17• 9 years ago

The capture would occur inside the router. You can just dump its ARP table which translates between MAC and IP address.

"If you're on your home network, this has no impact what so ever." Yes, I'm fairly happy with my own tracking policies :D

rlpb• 9 years ago

Actually, this is no longer true. An autoconfigured IPv6 address can leak your MAC address, depending on your settings, as one mechanism for autoconfiguration embeds your MAC address right into your IPv6 address.

just1nn2• 9 years ago

I have Fibre to the Home at 1Gb/sec, but so far, they do not support IPv6. That's something interesting for me to look into though, so thank you. I was providing ADS-B flight data to a website, and then I realized that they were posting my MAC, my NAT'd IP, and my GPS location to the world. That L7 will get ya every time.

partycoder• 9 years ago

Your router MAC address is tracked by Google Location services. They do this with their wardriving vehicles and from Android phones.

chatmasta2• 9 years ago

Yes and even if you changed your Mac every day, your neighbors probably wouldn’t. So google can still see the three routers around you, look up the gps those routers have been seen concurrently with, and know where you are.

paulfurley17• 9 years ago

Not sure if I'm missing the point here... if I were using Google Location services, wouldn't that mean I was giving Google my location directly? Why would they need to use my MAC address?

krrrh• 9 years ago

It’s worth noting that iOS has randomized MAC addresses in WiFi probes since iOS 8.[1] As far as I know your real MAC address is exposed upon connection. I’m curious to what extent other vendors have implemented this strategy.

[1] https://arstechnica.com/gadgets/2014/06/ios8-to-stymie-track...

lawl• 9 years ago

That doesn't address the issue of you being tracked by mac when logginh into a hotel, as you said the real mac is used when connecting.

This only addresses tracking when your phone is in the pocket and sending probe requests to scan for AP's.

blitmap• 9 years ago

So... this post is about Ubuntu, but if we're going down that road: https://medium.com/@philipn/want-to-see-something-crazy-open...

aaomidi• 9 years ago

Are there any demos for this still available?

developer2• 9 years ago

Unfortunately the iOS support is a sham. I tested myself, and the rumors that iOS does not randomize MACs turns out to be true. Not only does it not simply change over time, it doesn't even change when you restart the device. I walked around for a week, and my MAC never changed.

Apparently, if it ever works at all, you have to run settings that nobody uses - including, iirc, not being connected to a cell tower. I used to spread the same FUD of "iOS does this!", but the truth is it's a lie.

zaarn• 9 years ago

It only uses the random MAC for Wifi probes, no router I know of records these but they can be sniffed. Any real connection uses proper MAC.

If you want random MACs everytime I recommend Linux + a fairly recent NetworkManager.

racer-v• 9 years ago

Note that your MAC address is only one part of the identifying information your computer gives to the DHCP server. For another approach check out DHCPcAnon:

https://github.com/juga0/dhcpcanon

You can contribute to the development of this project by helping to integrate it with your favorite WiFi manager.

paulfurley17• 9 years ago

Identifiers in DHCP requests is a really good point, thanks for raising this. I'll do some captures and see what my client is revealing.

scott_karana• 9 years ago

I wish their readme would show some examples of leaked information from reference dhcp clients, so we could tangibly see why that's an improvement.

jimmaswell2• 9 years ago

I recently noticed that Windows 10 has that feature too, which came as a surprise to me

throwaway6138342• 9 years ago

Confused, I thought many chips (like some/many Intel ones) don't let you spoof the MAC address?

Avery3R• 9 years ago

There's a prefix or suffix for Mac addresses that means self administered. A lot of them will let you change it if you use that

SubiculumCode• 9 years ago

Is there a good (trustworthy) one for android?

emmelaich2• 9 years ago

What about bluetooth? And does NFC have an hardware address?

JepZ• 9 years ago

Btw. if you want to use a random mac address just for one specific network you can simply add the following to the [wifi] section of the config file for that network (/etc/NetworkManager/system-connections/):

  cloned-mac-address=random

That way every time you connect to that network you will have a new, valid mac address.

paulfurley17• 9 years ago

I look forward to it when Ubuntu LTS includes a more recent NetworkManager :)

“I learned that NetworkManager 1.4.1+ can do MAC address randomization right out the box. If you’re using Ubuntu 17.04 upwards, you can get most of the way with this config file.”

L_user6871• 9 years ago

How do you do that? </p>

Randomize your WiFi MAC address on Ubuntu

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