Running a Buffer Overflow Attack - Computerphile

Making yourself the all-powerful "Root" super-user on a computer using a buffer overflow attack. Assistant Professor Dr Mike Pound details how it's done.
Formerly titled "Buffer Overflow Attack" -Aug 2021
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This video was filmed and edited by Sean Riley.
Computer Science at the University of Nottingham: bit.ly/nottscomputer
Computerphile is a sister project to Brady Haran's Numberphile. More at www.bradyharan.com

[@tristant9686]

You can see he is very excited to tell this.

[@minecraft9260]

Tristan T I'm excited to learn this.

[@germangamingvideos6069]

@@minecraft9260 Me too

[@matze3596]

Frist time he can show what i spend his time on...Most people would not listen maybe cause they dont understand or maybe because they believe its something illegal.

[@buzifalus]

Because people are usually not interested or afraid of complex computer stuff

[@iraianbu3388]

May i know what content is on cat shell_code

[@MaxJNorman]

I really like this guy

[@TheCFJB]

I'd 100% agree.

[@gregoriysharapov1936]

Absolutely, max!

[@benchiang8235]

Me too, he's cool.

[@GodlyOne123]

It's refreshing to see positivity and enthusiasm towards typically dry subjects. This whole channel is great, but this guy in particular is probably their most enjoyable to watch.

[@ashleybishton742]

Dude can hack anything I bet lol. He could devastate a system lol

[@aadeshsalecha4951]

This was by far the best video..... Normally Computerphile tries to address a wider audience, but I personally would like to see more of these kind of in-depth videos.

[@kipchickensout]

exactly

[@CP-hd5cj]

Check out liveoverflow if you like this. He has tons of similar stuff, and decently in-depth

[@dvorak2676]

this is an introduction

[@iraianbu3388]

May i know what content is on cat shell_code

[@cheesescrust5399]

Dvo rak yeah I learned how to do basic stack overflows and run stack overflows back in the XP days, but I never learned in depth, complex attacks. I learned enough to run a debugger, find the memory address, write a nopales, etc but I never got deep enough to learn heap spraying, etc. They can get really complex now to bypass ASLR and other measures. I am trying to revisit this and learn more!

[@ElagabalusRex]

I would love to see a series on micro-architectures, machine code, and assembly

[@TheRomichou]

+ElagabalusRex Agreed!

[@Funderpanda]

and micro-waves!

[@akam9919]

Yes!

[@kanpitcha54]

please!

[@AbuDoujana]

@stephen schneider it may be tricky but it is definitely not 'insanely hard'... U just need to know at least the basics of forward programming ( C programing for example) and you can start from there, i would say i love it more than any other field but everyone has an opinion

[@edgeeffect]

The sledge/bomb animation is BRILLIANT!

[@seanski44]

Thankyou! I was pleased with that one ;)

[@FreeStuffPlease]

It made me laugh :)

[@ItsNotJustRice]

I know this particular video was years ago, but this guy is actually fun to watch. I'm terrible at learning, but he makes sense of a lot of things without dragging on the boring part.

[@Stopinvadingmyhardware]

Are you that mad at someone you don’t even know?

[@Soedmaelk]

@@Stopinvadingmyhardware You replied to the wrong guy

[@sickerpuppies]

"It's meant for ethical hacking, let's just make that clear" - Mike Pound, 2016

[@ashleybishton742]

Only if you know how to use the scripts.

[@charlieweberlv]

That’s like trying to say this is an ethical shot from a gun to somebody’s body, it’s a hack.

[@thegoodkidboy7726]

@@charlieweberlv People who find exploits and report them are important to the security of many systems. Companies hire penetration testers to try to break into their systems, so these issues can be fixed. Watch the footage of L0pht testifying before the US senate in 1998.

[@davishall]

@@charlieweberlv Not at all. To be able to identify bugs, one must be able to think like a malicious hacker and have the same tools as a malicious hacker. Without ethical hacking, there would be a lot more unethical hacking.

[@slingshot99]

@@charlieweberlv You have to be able to disassemble something to understand its flaws. That's what ethical hacking essentially does.

[@Elite7555]

Absolutely brilliant demonstration. All universities that I know teach C/C++, but they don't teach the essence of software security, which should be pounded into every student's head right from the beginning.

[@NightLife094]

In my university in germany, they taught us these. But i mean the courses are called cybersecurity and reverse engineering

[@lawrencelim6890]

@@NightLife094same. The info was taught in an intro to cyber course which made us do a lab that required us to attain root access using buffer overflow just like in the video.

[@ButzPunk]

This was brilliant. More like it, please!

[@cloveramv]

Powerrrrrrrrrrrrrrrrrrrrrrr BUHAHAHAHAHAAHAHA whoami . . I am root baby.

[@iraianbu3388]

May i know what content is on cat shell_code

[@colossalbreacker]

I'm a cs major, but I don't normally like watching cs related youtube channels. These videos are awesome though, some of them are things I thought I had a decent grasp on and I end up learning something. I also love how happy Dr. Pound seems when he is talking about something, you can tell he really likes what he does.

[@sivalley]

To err is human, but to really foul things up requires the root password. -Unknown

[@U014B]

Love it.

[@sophiacristina]

It was Aristotle!

[@kbs1212]

sivalley Stealing-no, borrowing this

[@xBZZZZyt]

Or SUDOer's password.

[@masonhunter2748]

To err is human. -Grammarly

[@geonerd]

Mike has a certain Dr. Evil vibe in that he clearly enjoys writing "Malicious Code." :)

[@Anvilshock]

Nice presentation, thanks! It would be even nicer to have the stack video segment made clickable, given KZbin's tendency to "Suggest" everything but related videos.

[@Computerphile]

+Anvilshock I'll sort that! >Sean

[@Anvilshock]

***** Much obliged, thanks!

[@zavvie809]

+Computerphile I suggest heap sort for that. :)

[@MamboBean343]

+Computerphile Still not really fixed. It's currently neither a card or an annotation.

[@ChaimS]

+Anvilshock Also, it would be awesome if it was mentioned where in the video he talks about them, since we may not necessarily have 10-15 minutes to watch the whole video.

[@__-xl1zi]

Everyone else: *makes a 20 char buffer* Mike: "We allocate a buffer that's 500 characters long"

[@username17234]

You need the buffer to be big enough to be able to comfortably hold your machine code plus a hefty padding for memory address variations.

[@dicksonZero]

still wondering how he is going to type all 500 characters until he pulls out his python

[@cheesescrust5399]

Eduardo I didn’t think it matters. I thought even small buffers could be exploited because the exploit payload just overflows and gets thrown into the stack. As long as you nopsled is hit by the pointer it just keeps running until it hits the return address which jumps to the shell code? Is that not correct?

[@rampage_sl]

@@dicksonZero I see what you did there

[@mu11668B]

Well... If I'm not writing codes for dev boards that has memory capped at few KBs, I usually allocate a lot more, like 4096 bytes. It has hardly any drawback for machines with GBs of RAM and lowers the risks of writing data beyond the buffer zone.

[@dantesalighieri]

The way this man explains things is absolutely DIAMOND.

[@smtkumar007]

youtube algorithms are like now this guy has just finished watching bootstrap in 1 hours & that more than enough to recommend him buffer overflow attack videos

[@DFX2KX]

messing with, and forcibly messing with the stack is the source of a few old school console hacks if I recall, particularly on NES games. You write memory by doing very specific things to set certain memory values in an unusual way

[@hamstsorkxxor]

Pokemon! If I remember correctly, that missingno nonsense in Pokemon Red was a stack overflow.

[@UmVtCg]

The game genie does this

[@ns2304]

Think its how PS1 and onwards did it as well. Gameshark and Gamemaster ripped the values off the game corresponding to a particular attribute. Then you tweak the code to get outcome like inf items, inf health etc. Never knew this was the science behind it hah

[@realeques]

i love how he explains every topic like its the best in the world... i could use him as my personal coach !

[@qgysugfq3935]

This hits especially hard since I just finished my assembly and computer systems class. Great video!

[@fernandojackson7207]

Ok, I was finally able to translate from Brit: "Buffalo, Buffalo at Work" =="Buffer Overflow Attack" Great video and explanation.

[@another-person-on-youtube]

"Can't type while people are watching." I'm not the only one!

[@MrJoao6697]

What a video! Great job on explaining this attack, I'll definitely be looking forward to learn more of this as I get into assembler at University!

[@timm9301]

I have studied exploit dev for a number of years and this is by far one of the best explanations ever! Keep it up!

[@anyonetube]

the first 3 minutes of video give me more efficient information than any other videos i watched about this title

[@34521ful]

Just a slight error for future viewers, at the 7:10 minute mark, he points from "a" to the start of "buffer". What he meant was that we are at "ebp" to the start of the buffer is what sub $0x1f4, %esp does :)

[@mustafadurukan6893]

So the buffer starts from esp minus 500 and the buffer progresses towards ebp, right?

[@xSCOOTERx2]

Had this for a homework assignment. It was quite hard to understand how to manipulate the stack at first, but this video helped a lot.

[@itissmallagain8002]

currently have this as assignment

[@JaceLansing]

Man! How am I only finding your channel now!? This was great. Thank you for taking the time to put this together.

[@jonahansen]

Damn! Excellent presentation on how stack overflow exploits work! No hand-waving; a complete demonstration of how it's done, down to aligning the return address and the no-op sled mitigation.

[@x1g5dj7dh4]

This was amazingly informative, especially for someone not using Linux. Well done!

[@MiSt3300]

Apart from the attack, it's so interesting to see how the computer actually processes the programme... I mean, I never really thought about it, that all the functions and returns and variables have to be stored somewhere and that it has to know how to execute it... I really like to think of a computer as a human being XD

[@IrishH2]

Fun fact, buffer overflows are where most of the famous glitches in the original Pokemon games come from. From Missingno. to fighting Professor Oak, to getting a Mew in Cerulean City. All done through buffer overflowing and putting numbers where they shouldn't be.

[@williamdrum9899]

Interesting. Those games were coded directly in assembly though so I don't think they used stack-allocated buffers.

[@shumakriss]

Thank you! I've never seen this explained in its entirety and there are lots nuances that have always inhibited my own educational endeavors. Knowing GDB, assembler, endianness, no-op sleds, etc were all concepts I understood but could never completely tie together. Excellent video.

[@JaisMathews]

It would have been pleasure to sit in his classes. We need more professors like this.

[@lolbajset]

I absolutely love videos on things like malware, exploits and similar stuff, feel free to upload more of it if you can :D

[@cyberwithtom7714]

for years ive been reading and trying to work out the ins and outs of bufferoverflow i can honestly say this is one of the most simple and effective videos out there on BO well done and Kudos loved watching it (for the 100th time)

[@Acid113377]

probably one of the best computerphile videos yet. Thank you Dr. Pound!

[@eliausi9696]

Welldone on explaining this so well

[@hellterminator]

And this, kids, is why you should always sanitize your inputs.

[@michaeltorres1263]

+hellterminator HAHAHAHAAHA!

[@SUFHolbek]

+hellterminator Little Robby Drop Tables

[@hellterminator]

Simon WoodburyForget Interesting language. I'm probably gonna stick with C/C++, but Rust is definitely interesting.

[@jurepustoslemsek7882]

I watched this a long time ago, but after taking an Assembly class in uni, I suddenly completely understand what he did and why it works! this is an absolutely amazing video as it actually gives an incentive to continue learning low-level programming and such.

[@TheMagAirsoft]

Dr Mike Pound, i do not know if you know this but you are saving a lot of network security students with your videos on these subjects. They are incredibly informative and makes a whole subject comprehensible in the matter of minutes. A Great thank you.

[@gassnake2004]

Great video! There's a lot of virus "concept" videos that explain how they work, but not many that show the actual implementation and writing of specific attacks. More please!

[@athanoslee]

I like his playful manners and smiles. I think I have a crush.

[@nofrag25]

He s married bro

[@firstnamelastname7319]

I want him to overflow my buffer 😍

[@jscorpio1987]

Thibaud so? Are we supposed to intensively research a person’s personal life now to make sure they’re absolutely 100% single before we’re allowed to have an innocent crush on them? It’s not as if you can control such feelings and it’s not like OP was exactly sending the guy a marriage proposal.

[@kbs1212]

J T Maybe OP isn’t but I am. Marry me Mr. Pound

[@untilted9126]

I do as well

[@tommybenshaul3443]

a very good video, explains beautifully the why stack works and how to exploit a buffer overflow

[@DirkArnez]

Very clearly explained... I have been looking for a tutorial like this for about ten years.

[@furetosan]

Awesome video. Especially the bit about the no-op slope.

[@Tommus1997]

"I'm assuming you know what a stack is." *defines function*

[@Juasml]

When you know a lot about something, sometimes it's hard to tell when you're being overwhelming and when you're going too slow. I guess he just randomizes it to keep going.

[@dderudito]

Hahaha

[@jag831]

Haha that's why I love this kind of videos. "Look at this ebp register, for example. B stands for base and B is the second letter of the latin alphabet. It is allocated in 0x6404whatever5A in memory"

[@fetchstixRHD]

To be fair, there was the video on stacks which anyone who wasn't familiar with could go and watch, so there isn't [wasn't] much point of repeating what's been done already.

[@Tithis]

Studying for a security certificate and was having a hard time understanding exactly what was going on with the way they explained it in their videos. Your video really helped me understand it better, mostly by visualizing how the memory is laid out.

[@mad7227]

His best yet IMO. Love the level of detail and honesty enthusiasm of the topic 😁

[@VaultRaider]

These types of videos are better than the robots/drones stuff

[@anujmchitale]

Not for a person who isn't interested in SW security or programming in general.

[@navalkumarshukla9447]

I really liked the way he taught, didn't get it,but liked it xD

[@chris_1337]

This was AWESOME! More, more, more please! Dr Pound is a great teacher

[@lumin0l161]

Best explanation of a buffer overflow I’ve ever seen.

[@HavelockBanana]

yeah! A technical video :-) Nice to see some actual code on this channel (even though it's being explained in a simple way :) )

[@5upl1an]

The real question is, how can someone be so damn motivated at 7 in the morning?!

[@RonaldMcPaul]

Eating healthy breakfast cereals and grains.

[@xxxXXXCH04XXXxxx]

@@RonaldMcPaul yummy

[@hypernova2906]

the stack content visualization and the no-op sled animation were really awesome

[@__-to3hq]

I love how much this guy loves talking about all of these topics its awesome :]

[@GenGariczek]

More on similar topics please :)

[@saultube44]

The guy is quite smart and he knows his stuff

[@CryptoJones]

Dr. Pound, thank you for the brilliant explanation of this. I wish I had you to explain these things to me as an undergrad.

[@hoptimas5415]

Thank you guys for the video!

[@user-eh5wo8re3d]

very nice Video. would love to See more of this sort in the future

[@gegdim9307]

Fear not my friend! Botnets and iPhone decryption coming soon!

[@user-eh5wo8re3d]

Well that is a truly marvelous thing to hear. Am looking forward to it!

[@harleyspeedthrust4013]

Ignorant friend: "Why would you ever use Assembly?" Me: "..."

[@cup-of-char]

Greetings! I watched this video to help me understand buffer overflows in my binary exploitation class in university and it was really helpful. Thank you so much!

[@SaeedAlFalasi]

Iv seen a bunch of videos on the same topic BUT THIS BY FAR is the best explanation !

[@rchandraonline]

On the original diagram: Functions do not (normally) go on the stack. The stack is only data (including return addresses). With architectures having hardware support for not executing data (often called an "NX" bit), such as a lot of the Intel processors, trying to execute a function on the stack with the NX bit set would cause an exception, which in Linux in turn would generate a signal (something like SIGSEGV), and without a signal handler would kill the process. (Yay, memory protection!) oh...and I think you mean backslash x ninety.

[@Computerphile]

+rchandraonline I've a feeling that's what Mike was talking about at the end.... >Sean

[@rchandraonline]

***** , oh, yeah... As Mike says (paraphrasing), there are so many things which would make great videos on what goes on in GDB and assembly...simply fascinating how all that stuff was developed over the years.

[@JAN0L]

+rchandraonline Function code doesn't, but all the local variables used by the function go on stack, otherwise recursive functions wouldn't be possible.

[@stensoft]

+rchandraonline For running shell (or other simple tasks), NX bit is quite easy to workaround with return-to-libc attack. But that can be hardened with address randomization.

[@GegoXaren]

gcc -fstack-protector-strong -std=c11 foo.c -o foo

[@tiannimyers1204]

The more I learn about computers, the more I realize how easy they are. Great video.

[@Nekology87]

wow! such an insightful glimpse at how computers "think" and Dr. Pound you are so charimastic ^___^ thank you Computerphile for this video!! I'm just begining my programing education and this fills my cup with drive to push through learning the basics knowing later i will be able to excecute as my will wills

[@Denverse]

Today is the day I finally exploited a full buffer overflow attack to gain shell. Thank you Mike. And the animation is so helpful.

[@Dusk-MTG]

*Segmentation fault* Me: "Oh damn, I fcked up." Peter Parker: "That's exactly what we wanted."

[@GegoXaren]

and this, kids, is why strcpy is removed from C11. Many of the string functions were removed and replaced with safe versions in C11.

[@GegoXaren]

also use -fstack-protector, -fstack-protector-all or -fstack-protector-strong with gcc for non-time-critical stuff.

[@anujmchitale]

strncpy is the replacement. The n is a parameter asking how much to copy. If more than the buffer length being used, the function itself won't compile.

[@Aemilindore]

I truly love the method Cumputerphine explains things. These are very advanced concepts explained so simply. Hats off for your effort. I am a researcher in the field of WSN. But I truly love this type of work. I would love to know what research field are related to this type of work. Once again. Great explanation. Love your videos!

[@hannahwhitham3539]

I'm so happy this channel exists

[@taubrafi]

Kali!

[@ttttt_]

"there is nothing you can't do as root" except makepkg on arch :(

[@nik123true]

nice one xD

[@sauron1427]

but you can create a user with whatever password you like, su into that user and run makepkg. you can still get ANYTHING done if you have root access.

[@pedro.raimundo]

I LOLed.

[@cybrhckr]

and some programmes does not allow you to run on root :D for security reasons

[@Reth_Hard]

You can't run VLC on root :( But you can patch it easily :)

[@nikhilnarayanan5949]

This channel is by far one of the best....I made a computer application similar to chain reaction using the swing framework of java....I got a stackOverFlow error because of infinite recursion....this video really sorted me out....thanks!!!😁😁😊

[@Piotr3kM]

Great stuff, I love videos that actually show something working in practice, rather than just the theory. Moar pls!

[@timt.4040]

Very helpful! What is the gdb command (not shown on screen) to list the 200 registers at the stack point of -550?

[@jbrhsn8406]

Google it Pal!

[@abindieflasche100]

@@jbrhsn8406 what is it

[@zerozone1412]

@Tim Thompson did you find out what the command was? I need it😫 ..... thanks

[@jag831]

Something like "x/500xw $esp -550" could work. I may be wrong

[@anirudhsarma4233]

Can anyone explain why 10 duplicates of the return address was needed as "padding"?

[@Zeldon567]

As a frequent viewer of videogame speedruns, I know quite a bit about the uses of buffer overflow/underflow. Fun stuff.

[@pierreaupeix]

This was very interesting. More of this please!

[@Calin42]

when a video on the ROP chains? with ASLR on and nX :p

[@ryanofarrell186]

Video is 17:29 long. Mathematicians, unite!

[@tennicktenstyl]

What's so special about this? I'm not familiar with numbers and stuff

[@Keithfert490]

It's the smallest "taxi cab number": a positive integer expressible as the sum of two positive integer cubes in two different ways (1729=12^3+1^3=9^3+10^3).

[@tennicktenstyl]

Oh, that's nice.

[@sadrien]

Don't worry if you don't understand why that is important, because it really isn't.

[@Quantumoprh]

The quotient 0.58620689655 is used 731 times in this txt document: ftp://ftp.sanger.ac.uk/pub/1000genomes/zd1/ctcf/chip_seq_quantitation/rel_2012-09-21/cl.txt

[@kamoroso94]

This was an awesome video! I remember learning about this in class but not how to exploit it and see it in action.

[@MeditatingDennis]

I like how the guy gets excited and makes me excited aswell!!

[@amine250]

who's watching this after the discovery of the sudo exploit ? x)

[@loneranger4282]

what is the sudo exploit ?

[@amine250]

@@loneranger4282 Barron Samedit

[@marsgal42]

I'm guess I'm showing my age when I mention that this was how the Morris worm back in 1988 infected systems. :-)

[@jag831]

Cool! I was wondering on actual, real cases in which this has happened

[@emrekantar5003]

Might be by far the best explanation i’ve ever watched

[@michalski9141]

this is genuinely great content, very informative and well made

[@CreativeVery]

You know you're 1337 when you use Kali.

[@aeinarrkrigsson]

Black arch ftw

[@mustafakhalid9348]

Newbies think it's cool

[@alejandroflores7565]

Actually it's very handy, i've been pentesting and bug hunting for a long time and Kali is always my go-to.

[@bluekeybo]

How would the "hacker" get the correct return address? They'd have to run gdb and list the addresses like in the video? How'd they do it automatically without root access?

[@aneeshjoshi6641]

I think: Since every process works assuming it has the full RAM and in C you can get the address of anything using & you can probably get it.

[@chasehiatt5595]

Gdb doesn't require root access

[@bluekeybo]

@@chasehiatt5595 interesting

[@rrestoring_faith]

gdb is just a debugging tool. Can run it on any executable if you have permissions to execute that executable.

[@johnconnor7978]

The only truly knowledgeable bunch of geeks on the internet that also know how to explain what they know. You sirs earned by EIP hi5

[@jasonford2877]

This video explains it better than a $2000 course I've been doing in Cyber Security (which goes into far more than just BOF) Drawing it tremendously helped me understand it!

[@woutervandenputte1356]

at 13:40 which command exactly do you use to list those 200 registers at the stack pointer minus 550

[@nahue345]

x/200xg $rsp (i think)

[@chaoluncai4300]

i dont get why stack ptr minus 550 but not just 508 if the program stopped at the return address, can anyone explain it please ?

[@supernaturalswampaids8083]

Cover the iPhone/Apple/FBI issue!

[@Computerphile]

+Reck Tominvayed Can you wait til Friday.... :) >Sean

[@supernaturalswampaids8083]

+Computerphile Yay! Thanks for the reply as well! I'm a huge fan! ....but I used to be a small air conditioner. Had to :P

[@jasonneu81]

+Player Name If you used to be a small air conditioner and now you're a huge fan then you must have been an intermediate ventilation system at some point, right :D ?

[@tabeshforoughi1380]

Thank You Dr. Mike.

[@supermegauberful]

That's actually very well explained! Keep up the good work.

[@JadarDev]

zsh is an older shell that doesn't have protections?! I use zsh all the time, I prefer it over bash because it has plugins.. How is that an old shell..?

[@framegrace1]

+JadarDev Yeah, is maybe the newest one. (Is younger than bash,ksh,etc...) But lots of exploits use it, not sure why. Maybe is just a hacker preference. (Like using rar instead of zip)

[@unforkableonion5081]

+Marc Gràcia Those who are the geeks among geeks, use zsh...is a sign of distinction!! please try 7zip and forget the rest ;)

[@michaelpound9891]

Sh is also fine for exploits. You can't use bash though because it drops out of root as soon as it starts. Too secure!

[@pat5star]

Michael Pound huh? sh is is just a link to bash by default. Or you can set sh to to point to your shell of preference, but as far as I know there isn’t any shell called sh.

[@umarsalmanrao5]

13:53 which command did he use here? x/200x $(ebp-100) Was it this?

[@pratheeps3972]

Same doubt bro

[@yuvalweber5946]

i think he used this : x/200x $esp - 550

[@panman101mw3]

I don't know why, but this felt a lot more interesting than all the other topics he's talked about. Rock on!

[@0noam]

it has taken me at least 5 times the duration of the video and a lot of zapping around to understand most of it. but it was extremely instructive, so thank you.