Monthly Archives: April 2006

Security Reporting – how critical is "Critical"?

What’s the difference between these two vulnerability reports?


  1. Firefox “focus()” Memory Corruption Weakness
  2. Internet Explorer “object” Tag Memory Corruption Code Execution

Okay, so the first couple of differences are obvious – the Firefox one is “Not Critical”, as it is a “Denial of Service” attack; the Internet Explorer one is “Highly Critical”, as it allows “System Access” (execution of code).


Now, let’s look at the details – particularly, the original advisories on which these are based…


The Firefox bug: “can be exploited to corrupt the memory and cause a crash…“, “By manipulating this feature a buffer overflow will occur.


The Internet Explorer bug: “At first sight, this vulnerability may offer a remote compromise vector,
although not necessarily a reliable one.


Okay, so in neither one has a remote execution been demonstrated.  Each one allows the remote attacker to corrupt memory.  Why the difference in criticality?


Obviously, I’m missing something here, but I’m not sure what it is.  Anyone out there have a better clue than I do?

Banks and SSL forms

I just knew this message was going to get badly diluted as it progressed.


What Ullrich has ‘discovered’ is that banks provide the form to their users over a plain-text link – while taking the input from the form using an SSL link.


This means that your password is not exposed to the Internet in clear-text, if you enter it into your bank’s form.


However, it means that you have nothing to prove that you are really connected to your bank’s form, other than a vague feeling that you typed in the right address, so anything that comes back must be from your bank.


With DNS hacks, and viruses that replace or edit your host file, that’s not a guarantee of anything very much, sadly – so these days, you should want your bank to identify themselves via a certificate – and that can only be done through an SSL link.


How do you know if the form on your screen has been delivered by SSL?  That’s what the ‘padlock’ icon shows:



The only problem… you also want your password to be sent back using SSL, and currently, there’s no browser that I am aware of that will tell you that this is the case, or prevent your form details from traveling back unprotected.


[It’s actually a computationally “hard” problem – possibly even computationally “impossible”, so let’s not be too down on the browser vendors.]

Two-factor authentication – what’s not to like?

Steve Riley always makes me think, sometimes so much that it hurts.  Thanks, Steve.  His latest blog posting is about two-factor authentication, and he’s asking for input on what you (we) want from it.


First, a couple of examples on authentication.


  1. “I am Bill Gates.” – this is not authentication.  It’s identification.  The fact that it’s an untrue claim doesn’t prevent it from being identification.
  2. “I am Bill Gates, this is Steve Ballmer, he’ll vouch for me.” – this is not authentication either.
  3. “I am Bill Gates, you already know Steve Ballmer, well he’ll vouch for me.” – this is weak authentication.
  4. “I am Bill Gates, you already know Steve Ballmer well, he’ll vouch for me.” – this is strong authentication.
  5. “I am Bill Gates – last time we spoke, I told you my favourite colour was red.” – this is authentication with a pre-shared secret.
  6. “I am Bill Gates – see, I still have the signed business card you gave me.” – this is authentication with a token.
  7. “I am Bill Gates – watch as I ignore the $1000 bill you left on the couch.” – this is authentication by ability (only a small number of people can afford to ignore free money).

There’s an old saying that goes something like “You can authenticate with something you are (biometrics), something you know (passwords), something you have (SecurID etc), or something you can do (skills measurement).”  Or, to put it another way, “something you used to be, something you have forgotten, something you lost, or something you can only do when relaxed in a well-lit room.”


The biggest deal we find with two-factor authentication is that the authentication device will be lost, destroyed, mangled, forgotten, given away as a prize at a sales talk, swallowed, or will simply refuse to operate in the Alaska (or Adis Ababa) office.


So, the second-factor (and if you’re replacing passwords with the factor, it’s not two-factor, it’s still one-factor!) has to be rapidly recoverable, re-deliverable, overridable, revokable (and ideally, unrevokable when they find it in their other trouser pocket), etc.  If I lose it, can you get me another one in the five minutes before I give my presentation?  [And if you can override it, what’s to prevent a hacker from doing the same?] n


Then you have to consider the message you send your staff by giving them security devices. “With these, your account is secure.” This means that they will use those skanky, dirty, disgusting computers in “Fly-By-Nite Internet Cafes Incorporated (Under New Management)”, or the clean ones at the airport that scream “definitely legitimate”, to download salary data on your most-valued executives, to view listings of covert agents in life-threatening deployments, to investigate your proctology results, etc.


What about those of us that wear multiple hats?  The consultants, the guys with an extra job?  How many tokens are we going to carry around with us?  One password per job is already fairly complexificated, but now you want us to remember a password _and_ carry around a half-dozen “key fobs”?  Perhaps a SecurID, Smart Card, or similar token should be able to authenticate against multiple servers – servers that don’t trust one another, and will not share keys.


Have I forgotten anything else you expect from a second-factor authentication method?

ActiveX behaviour change causes seizures.

The new ActiveX change will, apparently, cause seizures, and prevent ActiveX controls from running at all until clicked on. At least, that’s if you believe TechWeb


Sadly, SANS chose this page, with its stunningly inaccurate and poorly worded description of the new ActiveX change, as their main link to describing what’s going to happen.


The real deal of the change is far simpler.  If you want to send mouse input (including “mouseover” messages), or keyboard input, to an ActiveX control, you have to select the ActiveX control first to ‘activate’ it.  That’s all – the controls will run; music will play, the pigs will still dance, but you just won’t be able to tickle them until after you click (or tab and space/enter) on them.


So, no, ActiveX will not cause seizures.

Immigration idiocy

I’m struck by how many people are shown on the news spouting claptrap about immigration reform.


The biggest offence, in my opinion, is to stand there and say that illegal (or “undocumented”, if you prefer) immigrants are law-abiding, tax-paying residents.


Okay, number one… they are not law-abiding, or they would have abided with the law that says they should not enter the country without documentation.


Number two… if they are tax-paying, then they have compounded their law-breaking on entering the country by filing a false tax return.  How do I know it’s a false tax return?  Because, as undocumented immigrants, they have no social security number, and therefore must be filing with a fake SSN – either one that’s made up, or one that already belongs to another person.


Oh, hey, that there’s identity theft, too.  Imagine the mess you’d get in trying to sort out your social security if that happens to you – particularly if the social security lot give you a refund for overpayment, and then discovers later that they shouldn’t have.


So, next time you hear of a “law-abiding tax-paying undocumented immigrant”, think to yourself “engaging in identity theft, filing false tax returns, and continuing to evade detection and prosecution for a crime already committed”.


I spent a lot of time, effort and money that I could ill-afford to legally enter this country, even answering, without giggling, the many stupid questions on the immigration form (“Are you entering the country with the intent to overthrow or subvert the government?”, “Have you ever taken part in genocide?”)


I don’t ask you to agree with me (hey, if I sway your political opinions, does that mean I’m engaged in “subverting the government”?), but I do ask that you consider that while there are certainly some appalling abuses of human rights by employers of undocumented aliens, that does not necessarily make it right that anyone who evades the law for long enough should get a free pass into the country, nor does it mean that these individuals are “law-abiding”.

The hardest working woman in IT

This is a picture of the hardest working woman in I.T.:



I know she must work hard, because not only is she in the front page of Webroot’s web site, but she’s also in several print adverts.  I’ve seen her in Global Knowledge’s adverts, and a couple of the ‘cheap adverts’ at the back of several trade journals.


Please include some links below of places you’ve seen her.

Signs your crypto is wrong.

Here are a few signs that you might be doing crypto the wrong way:


  1. You’re using a third-party library “because .NET keeps throwing exceptions”.
    Explanation: .NET’s cryptography routines throw exceptions when you are doing something wrong.  If you are getting exceptions, you need to figure out why.
  2. You are encrypting (or trying to encrypt) with the private key.
    Explanation: You encrypt with the public key, you decrypt with the private key.  You sign with the private key.  Yes, signing involves an encryption with the private key, but that’s the only time you should encrypt with the private key – and then, you should be doing the hash and sign together.  .NET will throw an exception if you try and encrypt data with a private key.
  3. You are decrypting (or trying to decrypt) with the public key.
    Explanation: see sign number 2.  If your protocol requires you to decrypt with the public key, except as part of a signature verification step, then it is broken.
  4. You are designing your own protocol, rather than copying from someone else.
    Explanation: Cryptography is hard to get right.  Cryptography needs to be done using published and analysed methods, to know that you are getting it right.  Everything you are trying to do with cryptography has already been done.  Copy from others.
  5. You have started writing your final program before finishing reading the book.
    Explanation: Most books discuss the simple concepts first, and the subtler concepts are left for further in the book.  If you start coding before you have met some of the subtleties, you will paint yourself into a corner, or you will release a half-finished piece of crypto.
  6. You are writing SSL code, but you do not know what “close_notify” means.
    Explanation: close_notify is part of the SSL protocol spec.  Without it, you don’t know if your session was interrupted by a forged closure.  It’s covered in chapter eight of the book I read.  See sign 5.

I expect to have more signs later.

Desensitisation

Sandi Hardmeier’s blog is always an interesting read.


Today, she talks about the risks of desensitisation, and the tendency of human beings to trust email from certain sources.


I tell all my users, “Don’t trust email attachments.  From anyone, at any time.”  No exceptions.  No “Unless you know/trust them.”


Do not trust email attachments.


It’s that simple.


Does that mean “do not use email attachments”?


No, it means that you should verify that any email attachment you receive is virus free, and that it was sent by the person you think sent it, and that you have a good reason to risk opening it.  A phone call to the sender will verify that the attachment was sent, and what its purpose is, so that you can gauge its risk.  A virus scanner will allow you to verify that it’s virus free (as far as the most recent update of your virus scanner is concerned).


If you trusted the email attachment, you would do none of this, and simply open it.  So, and I can’t repeat this often enough, never trust email attachments.

IDE ate my source code

A tale to chill the blood of developers everywhere: “My IDE ate my source code” [For non-developers, “IDE” means “Interactive Development Environment”, and is how developers like to edit source code.]


My attention was drawn to the line “I’ve been using Borland IDEs on and off for the past 17 years or so, and nothing like that has ever happened before.”


Quite frankly, I gave up using Borland IDEs oh, a little over ten years ago, because the IDE I was using did exactly that – ate my source code.


I’d typed in a bunch of new code, and wanted to test it, so I pressed the button to debug my code.  Of course, the code crashed, and this being 1995, and on Windows 3.1x, it took the operating system with it.


After I rebooted, it became clear that my last several hours’ worth of work had not been saved.  Say whuh?


The Borland IDE of the time would happily compile code without first saving it.  [My first thought was “how can it even do that?  The compiler works from source files on the disk, surely?”, but I confirmed that you could create and compile an entire application without it ever hitting the disk except as object and executable code!]


[How is this security related?  Let’s say you fix a security flaw, and make a bug fix elsewhere.  You test the code – the security flaw fix works, the bug fix crashes when you test it.  So you reboot, and go make the bug fix in a different place, thinking your security fix is still in place…]

Security Exposure – it’s your behaviour, not your system

Along the lines of the new theory of child-raising, where you teach that “Stranger” is a behaviour, not a person, I saw today this blog posting from the Microsoft Antimalware team.


It highlights that in a recent analysis of the results from the (Malicious Software) (Removal Tool)(*), the most frequently detected piece of malware by far ( more than 6 times ) is a Trojan that pretends to be a crack for various popular software, and makes itself available on various P2P services.


If there’s a system that is vulnerable to this exploit, it’s the human central nervous system.  Layer eight.  Between the chair and the keyboard.


If you’re getting infected by this, I have one question – why are you killing your system?


Here’s a (loose) definition of malware: untrusted code from unknown people.


Here’s what you download and run when you get cracks from p2p networks: untrusted code from unknown people.


Oh, and to join in another argument that’s raging right now, “untrusted code from unknown people” can also describe what you get when you install unapproved patches by parties other than the vendor / developer of the code that you’re patching.


Practice safe hex.  Always get your software from a trusted dealer, and don’t try to skimp on the cost of the software.


(*) As opposed to the Malicious (Software Removal Tool)