Hacking Websites with SQL Injection - Computerphile
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- Опубліковано 9 лют 2025
- Websites can still be hacked using SQL injection - Tom explains how sites written in PHP (and other languages too) can be vulnerable and have basic security issues.
More from Tom Scott: / enyay and / tomscott
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This video was filmed and edited by Sean Riley.
Computerphile is a sister project to Brady Haran's Numberphile. See the full list of Brady's video projects at: bit.ly/bradycha...
One of the better 'funny pictures' I have seen, was a numberplate on a pretty fast car, which had an SQL instruction to drop some tables... hello speed cameras ...
This is the St Pancras Renaissance hotel in London - great that they let us film after our original location fell through - shame they wouldn't let me use lights though! >Sean
"; DROP ALL DATABASES;
dammmit.
Simply: don't ever ever trust user input.
One finger: "Facebook was originally written in PHP"
Second finger: All other things.
Nice one.
He speaks SO LOUD... lol... I think the entire cafe knows how to hack websites by now...
Tom Scott is awesome! "If you can't explain it to an eight year old, you don't fully understand it yourself!" -Unknown Smart person
"It's a hack on top of a hack.... That's a hack, and we've had to put more on top of that, and more on top of that, and more on top of that."
It's a hack stack!
>"You can read people's passwords..."
Well hopefully they're hashed anyway
Oh Tom Scott, you always manage to make us feel just a tad bit more paranoid.
"It works, but it's clunky." - PHP in nutshell.
I literally came to the video to see if he pronounced it as "sequel" or S.Q.L.
I got my answer instantly! :D
"Shouldn't work any more but still does."
Just ask TalkTalk's IT department...
Amazing that he knows I'm a camera, I'm impressed!
Love the non ordinary video background. Nicely explained topic. Thank you.
I am familiar with SQL injections but it doesn't work on any websites that are worth messing with
The correct way to think about this: when you are writing code that generates SQL, you need to generate it according to the SQL syntax. When you inject a string into an SQL statement, you need to convert that string into an "SQL string literal". This is done by adding the quotation marks at the beginning and end and escaping any character that has a different meaning in an SQL string literal than in a plain string (backslashes, quotes, etc...). The SQL syntax specification shows you where these string literals are allowed in a statement. If you are putting an integer into your SQL, you need to convert it to an "SQL integer literal", which is usually done just by converting it to a string. (Not an SQL string literal-just a string.)
Really enjoy the lighting and setting of this one. Informative person as well. Seeing a large increase in quality on this channel and it's much appreciated.
Actually I love his passion for the language and the whole subject itself. You can practically see the fire in his eyes. great work helped a bunch
Good ol' Bobby Tables.
Oh this should be some nostalgic fun, I remember back in highschool when injecting some code into a text field and... this video is from 2013. This video is from 2013? This video is from 2013! How in holy hell could ANYONE leave such a vulnerable area of security wide open this long?
Description amended to be less PHP specific - he does explain using PHP though, however little the PHP specific content >Sean
Thanks for these videos... In my experience of web programming as an amateur, Security issues have never been something I have come across all that often. It's good to learn more about them.
Tom is so passionate about this stuff. It is truly amazing to watch him explain stuff.
This video is good but makes it sound if a website is poorly coded (so SQL injection is possible) that the database server has no security and is an open platter i.e if a malicious user attempts to run a DELETE, DROP DATABASE command they will be able to do this. If the security on the database side has been granted appropriately the user specified in the connection string of the web application will not be able to execute these commands. All users should only be granted permissions required to do the tasks they are going to use. There is no need for a web application needing to have the DROP ALL DATABASES or similar commands. Not trying to water down the risk just making it clear that the problem lies on the developer (code) and administrator side (permissions).
Great video. Had a web interview a few weeks ago where I needed to know what an SQL injection is, and while I did try and explain it with my limited knowledge, I learned a lot more about it from watching this video. Thanks for the upload, and I'd also love to see more of Tom.
"It really shouldn't work anymore, but still does" is the best description of SQL injection I've ever heard.
This guy is the most entertaining and easy to learn from guy on computerphile! More please!
Just got out of jail because i tried this 5 years ago. THANKS ALOT FOR THE WARNING TOM
This is a really tough thing to explain to non-technical people, and this guy did a great job of it.
Love how this turned into a PHP promotional video with our host feeling the need to justify his usage of PHP! :D
Going to show this video to our apprentice. He is going to learn SQL in school soon. Best wishes from germany!
Really liked Tom's way of explaining, I too would like to see more of him!
Python has taught me really well with strings and escaping. Of course Ive learned more than escaping and learn strings, but I still am thankful for learning it.
I love your channel name and the videos are great! It really satisfies my love of technology, but makes me wanna learn more!
Robert'); DROP TABLE Students;--
funnily enough, I got a SQL course ad for this video.
More of this guy.
I always wonder if the other people in the restaurant (?) cant help but listen in on the riveting conversation going on.
This guy is one of the best on your channel! Get more videos from him!
moar videos with this guy pls, he's amazing; he manage to output such concise information with ease
I liked this bloke, he's very passionate about the subject which helps him avoid the boredom that can creep in when listening to a talk on programming.
Excellent topic too; I'm neck deep in learning PHP at the moment, so I appreciate the heads up about the security risks.
I quite like the moody lighting, gives it a nice atmosphere, Tom was a joy to listen to aswell.
The lighting in this video is really good.
I don't understand who dislikes these videos, no matter what there are people who will dislike every video on youtube
PHP is only fun at the beginning.
I seriously love this guys enthusiasm
I really like this guy, very enthusiastic, reminds me of my lecturer for databases
This video is going to be the response to so many stackoverflow questions.
as hacks go there are worse ones *heavy sigh* - There speaks someone who has had to deal with them! I know that sigh all too well.
"...someone who uses Windows." The expression at 8:31 is priceless! :D
I love that he writes things on old continuous-feed paper.
Me and my friend always joked about naming a kid "DropTable" in our IS SQL intro course.
But I guess now I realized it should be something along the lines of: Frank";Droptable
9 minutes from him is better than 90 minutes from my lecturer :(
Thanks for the video, I have a much much better understanding of how this works now.
I'd love to see more about security from Tom, he just does a wonderful job explaining things.
How did you isolate his voice from the surrounding noise?
Watching Video: Ok lets not be stupid.
After video: LET'S SEND SQL CODES ON EVERY SITE WE KNOW!!!
There's a fix for this. It's called not using PHP
Awesome video! Personally, I think that HTML, Javascript and PHP should be taught in every high school worldwide, if for no other reason than the problem solving skills and understanding of how the internet works gained in the process. No offense to the other client-side and server-side scripting languages.
Yay Tom is back! Great video as always!
6:57 near flawless join in audio from a cut
niiice
Great info! SQL injection is a classic security flaw
SQL was designed under the name SEQUEL (Structured English QUEry Language), but Sequel just so happened to be a trademarked name of a UK company called Hawker Siddeley Aircraft so it had to be changed.
From that, we can assume both ways of saying are correct since Sequel was the name originally intended but "Es-Kyoo-El" is the amended one.
I freaking love Tom Scott, everyone should.
Great explanation, more videos with Tom please.
I told countless times to the other developer at work to write all the SQL in procedures, and not inline in the application, but he did not listen to me. Now he works in another company, paid better than me. After a security check in my company, all my applications pass clean without errors, and all his applications have errors, and SQL injection problems. Now I have to fix all his applications, to transfer his inline SQL code to procedures. How fun is that !!!
Yes, another UA-cam user suggested the same. I checked it out recently and it's really nice. Thanks.
Extremely well explained. Great job!
Gonna change all my code to prepared statements right now. Thank you!
Great vid !!
There is a lot of confusion about prepared statements at the moment.
It's more than string building for onwards processing.
The SQL statement is parsed and optimised for execution by the RDBMS.
The variable is inserted prior to execution by the optimiser.
In general, it's a good thing to prepare when you can. Just trust me.
Most DBAs will have a large list of their commonly executed statements.
It's safer and they gain some element of control over the SQL being executed.
This guy is phenomenal; more of him please!
SEQUEL was different to SQL and used for ~12 years before the 1986 ANSI spec for SQL, in which the correct pronunciation is specified.
It may be that the pronunciation was only even defined to avoid copyright infringement, but since it's in the spec the pronunciation is just as well defined as the "SELECT" keyword, for example. Just as you can't swap "choose" or "find" or "get" for "select" in a query, there is a pronunciation that is defined as correct and other pronunciations are non-spec.
I really like this guy, he speaks with passion and intelligence
Don't most websites send text through some secondary language's, like JS or something, function to clean the input before sending it to the actual database?
This is exactly what I just learned about in my database class today... Computerphile, are you stalking me?
This guy is great at teaching.
One of additional benefits of database prepared statements is they usually offer a performance boost in returning the data. Not a huge amount mind you, but it adds up. If you need more complexity in database queries than prepared statements can do, than any web application should be using stored procedures. It is this specific point that royally pisses off most web programmers, because they need to learn the internals of something else, and their easy money job just became much more complicated.
I know it's not the point of this video, but it's really nicely lit!
bobby drop table students anyone
Great video! i really enjoy listening to Tom!
i think i'm the first person to have watched this series in the last 6 years lol
Firstly, a clarification: MySQL is a program what listens at a certain port for commands. Basically, its like a web-server. A PHP simply has a library what simplifies interaction with mysql program to a bunch of commands. So, PHP and MySQL are two different things, and SQL Injection applies to MySQL not to PHP. As someone who coded on PHP for 4+years, I think that language at its roots is a mess. Only way to make PHP something, is to rewrite everything from a scratch PROPERLY.
He clearly said it wasn't just a PHP specific problem. Great video!
Of course, in some cases stored procedures/functions can be better, but that often ties you to a particular database/infrastructure stack.
It's a trade-off in your overall architecture. Lock yourself in with Stored Procedures, or be a little more flexible (useful in products you want to sell, especially to large businesses/enterprises).
I love the way his eyes turned when he says "...Microsoft Database..." lol
I am a professional database expert and I know that the language I am a specialist in, DB2, that 2 two things...
1 - This has been a well known security issue for many years, and any DBM or security expert would be fully aware of these specific issues
2 - Even if for whatever reason someone was able to input commands they shouldn't be allowed to input..
2A - There are restrictions on who is allowed to perform what operations and on which table(s)(and even which individual records). Even if someone was able to hack the command stream and input malicious commands, any reasonable database will have very easy to implement restrictions that make sure nobody could ever do or view anything they aren't supposed to, and CERTAINLY not do any sort of potentially seriously disruptful actions like deleting data or dropping all databases, lol. Just a very simple restriction on any potentially powerful commands to only the database admins would nullify any of these potential threats.
2B - Even IF something catastrophic was performed like "drop all databases" there are methods of restoring the database to previous states, not just by having BACKUPS saved somewhere, but by diagnostic logs that can be used to roll the environment back in time. I suppose it's possible to imagine a malicous attack that was smart enough and all-inclusive enough to delete all backups and relevant data needed to restore the environment, but just keeping a seperate copy of backups on a completely separate system would alleviate that possibility.
These sorts of practices make me cringe inside. I salute you for your continued efforts.
The real question in that case is what constitutes "its own program".
You can run JavaScript via a browser, but the JavaScript code doesn't have to call browser specific (e.g. DOM) methods. You could (at least theoretically) write a JS code that works equally with a browser or with a server system (e.g. Node.js) or a build system (e.g. Visual Studio's ".w32" files). The language is all the same in all those environments. Only the non-core APIs of the runtime differ.
You're right. For me, using PDO implicitly means "use it properly" i.e alway prepare the statements.
Thanks for pointing out.
Good point. All JavaScript execution is done in a JavaScript interpreter, typically written in C. But if you're going to make that distinction, then you might as well say the most common language is x86 machine language.
The recent ‘Super Mario World (1990)’ speedrun uses code injection in very fascinating ways that I don't understand. There is even a way to play PONG on the game using in-game sprites and complicated code injection.
Thank you. The analogy in the beginning is genius.
i am a greyhat hacker and always send this video to webmasters of vulnerable websites in the hope that they fix it
I'd like to hear more detail about other methods of injections. I've always been under the impression that properly escaping your inputs was enough to be safe...
Who's here in 2022 when PHP has largely been replaced by Server side JS?
Sequel? I prefer squirrel injection. Sounds a lot cooler.
And “proper handling” means query parameterization (prepared statements) - which was actually described in this video…
But you can’t do it with PHP’s mysql_*, hence the “easier in PHP”.
I don't know what Chris is, but his comment just indicates that he is knowledgeable about PHP.
"Prepared statements" - this is also called parameterized queries, right?
I want a channel only with this guy