The Attack That Could Disrupt The Whole Internet - Computerphile

[@JH1010IsAwesome]

I once tried a denial of service attack on my friend. I knew he has a 32 bit computer, so I tried to send him a Facebook message 2^32 characters long thinking that it would crash his computer (and possibly lead to a blue screen of death). My computer crashed before I could send the message.

[@ericsarason9099]

Somebody should make a video. 3 guys are sitting in a room. Guy 1 puts on a mask that looks like guy 3 Guy 1 whispers "Monlist" to guy 2 Guy 2 throws a huge stack of paper at guy 3

[@SafetyLucas]

And I though I was scary pulling a flash drive out without safely ejecting it.........

[@razielhamalakh9813]

I was gonna tell you guys a joke about UDP, but you might not get it.

[@spazmaster6731]

A funny story from fall semester during the 2020 pandemic: because my university's classes were all online, one of my professors set up a website on a server he physically owned in his basement that he would upload assignments on. Turns out that was a bad idea because after every class when he would give us this week's assignment, he would get kicked offline from every student downloading from his server at the same time.

[@Lttlemoi]

This reminds me of a project we had to do for University. We had to build a database driven web application. However, in order to fill our database, we were required to get our data from websites. In the end, it turned out that at least 5 groups were mass scraping the same website during a few weekends. Even though we never meant it to be a DOS attack, the poor server was in trouble.

[@GtaRockt]

Tom Scott is to computerphile what James Grime is to numberphile

[@mvl71]

"Monlist!". The force of his disgust towards this command cracked me up no end! You just got yourself a new subscriber. Well done!

[@BlackhartFilms]

Tom Scott is by far my favorite person they interview on Computerphile

[@5nefarious]

Yeah. It's especially funny how worked up and passionate he gets about some things.

[@greenstonegecko]

"What time is it?" Server: *You want to know the time?* Server: *You want to know the time?* Server: *You want to know the time?* Server: *You want to know the time?* Server: *You want to know the time?* Server: *You want to know the time?* Server: *You want to know the time?* Server: *You want to know the time?* Server: *You want to know the time?*

[@Koseiku]

haha i love this guy. he is always so energetic.

[@tomlloyd2603]

Koseiku he has his own youtube channel - Tom Scott He's brilliant :D

[@eagle56786]

Tom Lloyd Ha. I thought he looked familiar.

[@Buzzy913]

Why don't we just remove Monlist?

[@bluekissedgalaxies]

i love how into it tom gets with the drawings

[@bluephreakr]

I love how angry Tom gets over this subject. The _passion!_

[@Envinyon]

I love this guy. He always sounds so excited when he's talking.

[@n6i9k4a]

His passion is addicting.

[@stephenrowley4171]

n6i9k4a He has the rare talent that he's passionate about a subject but also has the ability to communicate that passion to the layman.

[@Trirosmos]

All of Computerphile's videos are cool and all, but.... Tom is just amazing!

[@Br3ttM]

That "monlist" command sounds like something that exists for debugging, and should require special permission to use. Even without the DoS attack part, it seems like a massive privacy/security violation to just let anyone anywhere ask for a list of everyone who has accessed something. My guess is that if it wasn't just an accident that it was left in, they left it in because removing it would break something. "We can't fix it because something else needs it to stay exactly the same" is a thing in programming.

[@Max-bh8tg]

More of tom please, his enthusiasm keeps you glued to the screen.

[@cebsaid2932]

I like to imagine someone setting this up but forgetting to spoof the return and destroying themselves

[@siloPIRATE]

7:06 what do the other people in the building you're in think when they see you randomly scribbling and shouting 206 times? 😂

[@newgoredan303]

The fax paper to computerphile is like the brown paper to numberphile. Same for Tom Scott and James Grime

[@thisisnootnoots]

"I approve this stream being sent to me"

[@TheDoubleBee]

Two things I'd like to point out: 1. You can spoof the IPv4/IPv6 address for any IP-based protocol (TCP, ICMP, IGMP, etc.), not just UDP. 2. It's the ISP's job to drop packets that have a spoofed source address as they know exactly where the packet came from (based on MAC address), and even the big routing services have some level of detecting whether or not a source address is spoofed.

[@jaronfeld123]

I just found a new favorite channel. This guy loves what he does.

[@345derder]

I swear this guy I could just listen to him all day

[@Bluelemonzz]

Thanks for explaining the difference between TCP and UDT. I didn't know it was that simple. Now I know why the setting on my surveillance system is the way it is

[@vinkuu]

I've been a programmer of web apps for the last 15 years, and I like to consider myself more security-aware than the common developer, but this was actually new information for me. Thank you for sharing the knowledge.

[@PelegTsadok]

This guy makes me feel bad for a computer...

[@davidsweeney111]

I have to say I lean more to the chemistry side of the Brady universe, but I have to say I am completely riveted to watching this guy, he is so enthusiastic about his subject and so interesting to listen too, more please!

[@NourSelim0]

Tom Scott is back on Computerphile! YAY! :)

[@Quasihamster]

amplified distributed DoS? Yep, I get it. When you try to kick the internet's butt, be sure to wear ADIDoS!

[@Catnugget76]

More videos with this guy please. He explains everything so well

[@jochemvanl]

Very very good explanation! I work for a company with a reasonable sized network (couple of gbits) and own datacenter. For a while now we get multiple abuse reports a day for exactly this type of attack. Sending in these abuse reports is actually useful, as we will block customers after receiving too many reports and not seeing any action on their part.

[@Chrispmiller84]

It sounds like you work for a server/VPS provider. If that's the case, you should look into some automated network monitoring software. Depending on your infrastructure there's most likely free ways of doing so, and if you're company's a decent size, it could afford the cost of some of the better solutions. In the long run, you'd save money from having to manually deal with those situations. And who knows... Maybe management would be appreciative of your recommendation. Might get a nice bonus/raise? :)

[@jochemvanl]

Chris Miller thanks for the suggestion. I might just look into that.

[@tech-kyle]

An an employee of a local ISP, we've been seeing these NTP attacks on a high-bandwidth customer of ours for some time now. We definitely notice. I believe we've simply blocked NTP from outside sources and are only allowing a select few popular ones, but that's slightly above me.

[@lloydnone]

And that is something you might not have known! Great Video! Thank you very much!

[@caradu9973]

He is an excellent orator and teacher!There is a lot I don't understand until explained the right way... I'm sure a lot of people feel that way. Thank You!

[@legendofFranktheTank]

ive watched so much computer file, tom scott, matt and tom, and ashens, that youtube seems to genuinely think im british, and is now showing me ads for companies that dont exist in america

[@MZZenyl]

Really good video. I love Tom, he's so enthusiastic! :) Also, he talks about topics that I find very interesting (not that I'd actually follow any of his "tips", I just find it interesting). :)

[@Lolloz89]

Actually you can do a couple of things: 1) Replication 2) Distributed Caching 3) Content Delivery Networks (a.g. Akamai) Theese are all expensive things, but if you are under a DDoS attack, you probably have enough money to pay for these services :)

[@gadgetpilipinas]

Thanks a lot for this, Haley Joel Osment! Seriously, this is highly informative and worth sharing.

[@Ledon177]

This guy really has a natural talent for teaching. I had never been interested in computer science until I started watching his videos.

[@vipermagi5499]

I love this video because the only way I know of to truly raise security in this very attacker centric world is to raise the base knowledge of the average user.

[@thesickandwounded]

love when this guy explains!

[@aaronhsyong2]

Turned Closed Captions on. Saw [furiously scribbling] at 7:03. Nice

[@HampshireBrony]

When you started talking about TCP vs UDP, I was thinking of a new name for the reflected DoS via SYN flood. That NTP thing is pure evil! Sounds like a command that was put in to an early ntpd for remote testing/diagnostic/logging and ended up staying in

[@BhargaviCN]

The person who inserted "MONLIST" command in the protocol, is THE Culprit/Hacker! While misguiding you as "This is one useless command", he got way of hacking forever! Otherwise "last 600 users? Really? 600?", come on, you don't need Sherlock Holmes!

[@stalingra11]

@DerpTrolling on twitter currently holds the world record for the biggest DoS attack ever, it maxed out at over 420Gb/s and was against a company who wanted to test their infrastructure...They also delayed the customization packs for CoD by knocking the DNS servers that send the files, as wekk as every single LoL server, which is why they have had so much down time recently...

[@kapin0s]

Thanks Tom! Another great video with a really interesting and also terrifying topic.

[@THEGREATONE420]

so many different attack vectors exist in the tcp/ip stack. we are sitting here talking about host to host but the real fun begins when you start attacking the routers and routing protocols.. not that I'm in to that but the potential is huge.

[@Edgewalker001]

I actually remember that back during my school days there was this script you could run called a flooder that did pretty much this, and if you picked the right port to send traffic to on those old windows computers they not only lost all internet connections but also instantly crashed to bluescreen. I remember having a lot of fun with THAT on my school's intranet... =p

[@louisburke8927]

All the experts are so well spoken.

[@Charbthabowz123]

This man, should have his own T.V show!

[@Ultima2876]

Charb thabowz He does, it's called Gadget Geeks.

[@GypsyBackwards]

computerphile needs to have tom Scott on more, his videos are great!

[@BlackSkorpion0]

This is a great video, He explains the concepts very well.

[@HadienReiRick]

Truly, I think the only way to defend against DoS attacks is to improve the protocol itself. For instance UDP could handshake every once in a while, with the receiver sending a single "flag" saying that you can continue with the streaming. This will not only stop DoS, but could also save server bandwidth since the server will know that it doesn't need to keep sending packets to a recipient that doesn't want to listen (this would greatly improve the stream quality of sites like Justin, Twitch, Hulu, and Netflix). And the recipient can effortlessly let only one UDP transfer through, or none at all. another protocol idea is that when a server receives a request for a large amount of data (TCP), or just always (UDP), it 1st sends a "handshake" confirmation to the destination to make sure they really want it. This solves 2 things as one the server can ignore duplicated requests from the same "source", and again save even more bandwidth if the source turned down the handshake. There may even be a "timeout" flag included so that even the confirmation handshakes themselves aren't spammed. The only way a criminal could bypass this is if they hack the actual servers themselves.

[@SpringgyHD]

My IP is 192.168.1.1. a lot of people say they have the same IP but i thought IP's were only for one router/household. help?

[@ahmedabdelmalik-3050]

knowledge is priceless

[@MrVicke03]

I think that just happended...

[@Col_Crunch]

I would love to see a feature-length Documentary (60-120mins) made by the computerphile guys! I imagine that it would be amazing.

[@IanM0rris]

How did I not know about this beautiful channel?!?!

[@UnknowinglyDerpy]

Meanwhile in captions: [SCRIBBLES FURIOUSLY]

[@brianpso]

Wow! I don't really know what it is, but it's been a while since I watched this channel because of college stuff, and I feel like something changed on the transictions or the camera motion, that really make me get more concentrated on the video. I just loved his explanation, thanks so much for this video.

[@garenyo]

i really love this channel and the explanation of Tom Scott is really great. No matter what topic he is telling.

[@SleekMouse]

"How can you protect your servers? The easiest way to update to NTP version 4.2.7, which removes the monlist command entirely. If upgrading is not an option, you can start the NTP daemon with noquery enabled in the NTP conf file. This will disable access to mode 6 and 7 query packetts (which includes monlist). By disabling monlist, or upgrading so the the command is no longer there, not only are you protecting your network from unwanted reconnaissance, but you are also protecting your network from inadvertently being used in a DDoS attack."

[@stevensong6909]

There is such amazing content on this channel.

[@callum3651]

ok wtf is there to dislike about this video??

[@yzf]

Sorry if this won't make sense, but can't that monlist type of communication/request be blocked by firewall? Doesn't it have some specific attribute that could be set to firewall rules and firewall just wouldn't let it through?

[@StaffanThomen]

Aww, I expected you to mention amplification attacks in the IRC protocol itself and was disappointed. (CTCP VERSION or INFO for instance) These were all the rage when I just got on to IRCNet.

[@Orxenhorf]

Where the pressure really need to get put is on Internet Service Providers to do egress filtering on the outer edges of their networks, and ingress filtering on anyone they sell or rent a block of addresses to. That would actually reduce spoofing instead of just chasing it from protocol to protocol.

[@akash.trehan]

How did Tom get "206" times the data....Also "206 x ?" What is the basic thing whose 206 times is being sent?

[@flastable9842]

In the 8 years since this video's release, has this issue been resolved at all? Even partially?

[@mrdeadguy34]

My internet died when you talked about you're Internet getting denied :/

[@JonathanGray89]

The problem with UDP is the fact that there is no absolutely no protection against source IP spoofing; Any ISP that the UDP packets are traveling through cannot verify the legitimacy of those packets. Therefore, any public UDP service which can send more data than it receives is vulnerable to (D)DoS amplification, and in fact it is extremely trivial to accomplish this. With my knowledge and $1000 worth of VPS (like Amazon Web Services), I could bring down a big site for a couple of hours and make headlines. I would never risk it though because that would trace straight back to me. The people who do these attacks in the real world use BitCoins and Tor or VPNs only so that they're much harder to find. I don't have any BitCoins, no use for VPNs, and I personally find it immoral and even childish to perform DoS attacks. I find the technicalities slightly interesting but, compared to real vulnerabilities, to me it's just child's play.

[@23Joe91]

This is really interesting because I've noticed that some sites have been acting strangely last few days

[@ashwith]

Please do a video explaining the heartbleed bug.

[@shackelfro]

I absolutely love these videos. Tom is the man!

[@wisteela]

Great info, and bonus points for the retro computer paper.

[@MrVljacks]

I love this guy..... so simply explained, well done...

[@PontusWelin]

Wouldn't it help to do something like greylisting at the NTP-servers? So if a request comes in for a monlist command, the server checks the greylist and if they aren't in it, it responds by telling them to try again later. I have heard it works very well against spam since spam bots don't have a reason to ever resend anything. They can just send another mail. Maybe it would work for this?

[@TechLaboratories]

Tom, insightful as always!

[@oliverguy3121]

Note that the title says "disrupt" not "take down"

[@carterknox3096]

Wow I just found this channel and I love it.

[@leocossham]

Amazing video, well explained and extremely interesting; subscribed.

[@Systemist]

Loving this channel! Thanks for the great vids! :)

[@AustinHarsh]

Nice video but fyi TCP doesn't require packets to be sent in order. It just makes sure that all packets are received at some point in time.

[@Seegalgalguntijak]

So basically, it's the bad guys which are creating the need to defend against attacks of any kind that help improve security on the long run. I find this an interesting thought...

[@everaven7925]

I really want to know where Tom can still find Dot Matrix Printing Paper.

[@skimask13]

Great video and thanks for the book recommendation!

[@JuanchosMRL]

That passion of his... Awesome video!!!

[@TheVino3]

It's scary to think that something so intangible and seemingly untouchable as the internet...could soon actually be very vulnerable.

[@starwarsfannl]

just curious how would one go about tempuarly destroying the intire internet? I am not a programmer jet but i would think it has to be a file witch would effect everyone on a router and needs to have a timer of how long it will last and needs to make a list of everyone witch is already effect to make shure it will not destroy the internet for ever. any got some ideas on this?

[@nadehi18]

Flash forward three years and we've seen 620Gbps attacks with zero amplification...

[@sammbo250]

If you are getting these attacks surely you could just disconnect from your internet and maybe turn your router off. Would that stop it?

[@twomorestars]

Tom Scott is awesome. Thanks!

[@siprus]

You should do a video about security through obscurity! (and why it is bad) It's such an important concept in information security (and it might make a good video too)

[@mintoo2cool]

MONLIST is used to know who have already synced their time, so that you don't send them a sync command again. it's not useless dude. it's very a useful command. It's funny how it's being exploited though.

[@JasperJanssen]

Took 'em two years to get to terabit level attacks.

[@StoryMakerZ86]

Best video yet!! and easy even for me to understand!!!!

[@l0stmarble454]

Thank you Tom! You make great tutorial videos! :)

[@ShadyPossum]

what, if any, is a legitimate use for IP spoofing? it seems like every time i hear it being used its in a negative fashion. but if its only for attacks and masking those attacks, why allow them at all?

[@armouredhen30]

Question: Couldn't you just unplug your ethernet cable / router until it stops? Maybe quickly change your ip? What works be the problem with that?

[@SondreGrneng]

For us lowly commoners that might not be a problem however, say you are Amazon, or Google, or eBay or any other widely recognized webpage. simply "unplugging your Ethernet cable!" is not an option and changing your ip might lead to people not being able to immediately find you either,