Question of the Week

QoTW #42: Would publishing a network diagram make the network less secure?

2013-01-25 by roryalsop. 3 comments

I chose this week’s Question of the Week, saber tabatabaee yazdi‘s “Would publishing a network diagram make the network less secure?” because this is a point which seems to be often misunderstood.

Saber asked this question because he had come across various websites designed to let people share their network diagrams and designs in order that others can comment on them and provide guidance and he wondered what the risks would be from this.

As an example, this diagram from provides IP addresses, host names and even descriptions:

AJ Henderson provided the very valid comment that security through obscurity is not security, but admits that any network will have some weaknesses, and avoiding giving this information to a potential attacker is probably advised.

My answer is taken from the experience of managing many hundreds of penetration tests. My take on it is:

having a map helps me target my attack, avoiding possible sensors, honeypots etc and aiming at high value targets or sources of information. This can speed up an attack immensely, reducing the defender’s chance of preventing it.

But the value from these sites is that you can have obvious mistakes pointed out to you – peer review can be a very valuable thing. So how can you do that safely?

To reduce risk, some steps you can take are:
  • remove addresses, function titles etc
  • only include sections of the network
  • post under an anonymous profile
  • include fake network sections

An attacker will still get information, but it hopefully won’t be enough to let them navigate your entire network.

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QoTW #41: Why do we lock our computers?

2012-11-30 by roryalsop. 2 comments

Iszi chose this week’s question of the week, Tom Marthenal‘s “Why do we lock our computers?” – as Tom puts it:

It’s common knowledge that if somebody has physical access to your machine they can do whatever they want with it, so what is the point?

This one attracted a lot of views, as it is a simple question of interest to everyone.

Both Bruce Ediger and Polynomial answered with the core reason – it removes the risk from the casual attacker while costing the user next to nothing! This is an essential factor in cost/usability tradeoffs for security. From Bruce:

The value of locking is somewhat larger than the price of locking it. Sort of like how in good neighborhoods, you don’t need to lock your front door. In most neighborhoods, you do lock your front door, but anyone with a hammer, a large rock or a brick could get in through the windows.

and from Polynomial:

An attacker with a short window of opportunity (e.g. whilst you’re out getting coffee) must be prevented at minimum cost to you as a user, in such a way that makes it non-trivial to bypass under tight time constraints.

Kaz pointed out another essential point, traceability:

If you don’t lock, it is easy for someone to poke around inside your session in such a way that you will not notice it when you return to your machine.

And zzzzBov added this in a comment:

…few bystanders would question someone walking up to a house and entering through the front door. The assumption is that the person entering it has a reason to. If a bystander watches someone break into a window, they’re much more likely to call the authorities. This is analogous with sitting down at a computer that’s unlocked, vs physically hacking into the system after crawling under a desk.

It removes a large percentage of possible attacks – those from your co-workers wanting to mess with your stuff – thanks enedene.

So – protect yourself from co-workers, casual snooping and pilfering and other mischief by simply locking your machine every time you leave your desk!

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QoTW #40: What’s the impact of disclosing the front-face of a credit or debit card?

2012-11-23 by roryalsop. 0 comments

” What is the impact of disclosing the front face of a credit card?” and “How does Amazon bill me without the CVC/CVV/CVV2?” are two questions which worry a lot of people, especially those who are aware of the security risks of disclosing information, but who don’t fully understand them.

Rory McCune‘s question was inspired by a number of occasions where someone was called out for disclosing the front of their credit card – and he wondered what the likely impact of disclosing this information could be, as the front of the card gives the card PAN (16-digit number), start date, expiry date and cardholder name. Also for debit cards, the cardholders account number and sort code (that may vary by region).

TC1 asked how Amazon and other individuals can bill you without the CVV (the special number on the back of the card)

atdre‘s answer on that second question states that for Amazon:

The only thing necessary to make a purchase is the card number, whether in number form or magnetic. You don’t even need the expiration date.

Ron Robinson also provides this answer:

Amazon pays a slightly higher rate to accept your payment without the CVV, but the CVV is not strictly required to present a transaction – everybody uses CVV because they get a lower rate if it is present (less risk, less cost).

So there is one rule for the Amazons out there and one rule for the rest of us. Which is good – this reduces the risk to us of card fraud. Certainly for online transactions.

So what about physical transactions – If I have a photo of the front of a credit card and use it to create a fake card, is that enough to commit fraud?

From Polynomial‘s answer:

On most EFTPOS systems, it’s possible to manually enter the card details. When a field is not present, the operator simply presses enter to skip, which is common with cards that don’t carry a start date. On these systems, it is trivial to charge a card without the CVV. When I worked in retail, we would frequently do this when the chip on a card wasn’t working and the CVV had rubbed off. In such cases, all that was needed was the card number and expiry date, with a signature on the receipt for verification.

So if a fraudster could fake a card it could be accepted in retail establishments, especially in countries that don’t yet use Chip and Pin.

Additionally, bushibytes pointed out the social engineering possibilities:

As a somewhat current example, see how Mat Honan got hacked last summer : In his case, Apple only required the last digits for his credit card (which his attacker obtained from Amazon) in order to give up the account. It stands to reason that other vendors may be duped if an attacker were to provide a full credit card number including expiration dates.

In summary, there is a very real risk of not only financial fraud, but also social engineering, from the public disclosure of the front of your credit card. Online, the simplest fraud is through the big players like Amazon, who don’t need the CVV, and in the real world an attacker who can forge a card with just an image of the front of your card is likely to be able to use that card.

So take care of it – don’t divulge the number unless you have to!

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QoTW #39: Why would a virus writer bother to check to see if a machine is infected before infecting it?

2012-10-26 by roryalsop. 0 comments

Terry Chia proposed Swaroop’s question from 2 October 2012: Why would a virus writer bother to check to see if a machine is infected before infecting it?

Swaroop was wondering if this would be an attempt to use files that are already present instead of transferring another copy to the machine, but actually it boils down to two main reasons – the malware writer wants the computer to remain stable for as long as possible, and there is competition between virus writers for control over your PC.

Polynomial wrote:

The less resources used and the less disturbance caused, the less likely the user is to notice something is wrong. Once a user notices something isn’t working properly, they’ll try to fix it, which might result in the malware being removed. As such, it’s better for the malware creator to prevent these problems and remain covert.

Thomas Pornin linked to the original internet worm, which did prevent networks and systems working because it didn’t carry out checks, and both Celeritas and OtisBoxcar supported Polynomial’s top answer with theirs.

WernerCD wrote:

Preemptive removal of competitors products, as well as verification of no prior version of my product, would help keep the system mine. As mentioned, the goal would be to keep the CPU “mine”. That means lay low and don’t attract notice.

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QoTW #38: What is SHA-3 – and why did we change it?

2012-10-12 by ninefingers. 0 comments

Lucas Kauffman selected this week’s Question of the Week: What is SHA3 and why did we change it? 

No doubt if you are at least a little bit curious about security, you’ll have heard of AES, the advanced encryption standard. Way back in 1997, when winters were really hard, our modems froze as we used them and Windows 98 had yet to appear, NIST saw the need to replace the then mainstream Data Encryption Standard with something resistant to the advances in cryptography that had occurred since its inception. So, NIST announced a competition and invited interested parties to submit algorithms matching the desired specification – the AES Process was underway.

A number of algorithms with varying designs were submitted for the process and three rounds held, with comments, cryptanalysis and feedback submitted at each stage. Between rounds, designers could tweak their algorithms if needed to address minor concerns; clearly broken algorithms did not progress. This was somewhat of a first for the crypto community – after the export restrictions and the so called “crypto wars” of the 90s, open cryptanalysis of published algorithms was novel, and it worked. We ended up with AES (and some of you may also have used Serpent, or Twofish) as a result.

Now, onto hashing. Way back in 1996, discussions were underway in the cryptographic community on the possibility of finding a collision within MD5. Practically MD5 started to be commonly exploited in 2005 to create fake certificate authorities. More recently, the FLAME malware used MD5 collisions to bypass Windows signature restrictions. Indeed, we covered this attack right here on the security blog.

The need for new hash functions has been known for some time, therefore. To replace MD5, SHA-1 was released. However, like its predecessor, cryptanalysis began to reveal that its collision resistance required a less-than-bruteforce search. Given that this eventually yields practical exploits that undermine cryptographic systems, a hash standard is needed that is resistant to finding collisions.

As of 2001, we have also had available to us SHA-2, a family of functions that as yet has survived cryptanalysis. However, SHA-2 is similar in design to its predecessor, SHA-1, and one might deduce that similar weaknesses may hold.

So, in response and in a similar vein to the AES process, NIST launched the SHA3 competition in 2007, in their words, in response to recent improvements in cryptanalysis of hash functions. Over the past few years, various algorithms have been analyzed and the number of candidates reduced, much like a reality TV show (perhaps without the tears, though). The final round algorithms essentially became the candidates for SHA3.

The big event this year is that Keccak has been announced as the SHA-3 hash standard. Before we go too much further, we should clarify some parts of the NIST process. Depending on the round an algorithm has reached determines the amount of cryptanalysis it will have received – the longer a function stays in the competition, the more analysis it faces. The report of round two candidates does not reveal any suggestion of breakage; however, NIST has selected its final round candidates based on a combination of performance factors and safety margins. Respected cryptographer Bruce Schneier even suggested that perhaps NIST should consider adopting several of the finalist functions as suitable.

That’s the background, so I am sure you are wondering: how does this affect me? Well, here’s what you should take into consideration:

  • MD5 is broken. You should not use it; it has been used in practical exploits in the wild, if reports are to be believed – and even if they are not, there are alternatives.
  • SHA-1 is shown to be theoretically weaker than expected. It is possible it may become practical to exploit it. As such, it would be prudent to migrate to a better hash function.
  • In spite of concerns, the family of SHA-2 functions has thus far survived cryptanalysis. These are fine for current usage.
  • Keccak and selected other SHA-3 finalists will likely become available in mainstream cryptographic libraries soon. SHA-3 is approved by NIST, so it is fine for current usage.

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QoTW #37: How does SSL work ?

2012-10-05 by Thomas Pornin. 0 comments

In this week’s question, we will talk about SSL. This question was asked by @Polynomial, who noticed that our site did not have yet a generic question on how SSL works. There were already some questions on the concept of SSL, but nothing really detailed.

Three answers were given, one by @Luc, and two by myself (because I got really verbose and there is a size limit on answers). The three answers concentrated on distinct aspects of SSL; together, they can explain why SSL works: SSL appears to be decently secure and we can see how this is achieved.

My first answer is a painfully long description of the detailed protocol as it appears on the wire. I wrote it as an introduction to the intricacies of the protocol; what information it contains must be known if you want to understand the details of the cryptographic attacks which have been tried on SSL. This is not much more than RFC-reading, but I still made an effort to merge four RFC (for the four protocol versions: SSLv3, TLS 1.0, 1.1 and 1.2) into one text which should be readable linearly. If you plan on implementing your own SSL client or server (a very instructive exercise, which I recommend for its pedagogical virtues), then I hope that this answer will be a useful reading guide for the actual standards.

What the protocol description shows is that at one point, during the initial steps of the SSL connection (the “handshake”), the server sends its “certificate” to the client (actually, a certificate chain), and then, a few steps later, the client appears to have gained some knowledge of the server’s public key, with which asymmetric cryptography is then performed. The SSL/TLS protocol handles these certificates as opaque blobs. What usually happens is that the client decodes the blobs as X.509 certificates and validates them with regards to a set of known trust anchors. The validation yields the server’s public key, with some guarantee that it really is the key owned by the intended server.

This certificate validation is the first foundation of SSL, as it is used for the Web (i.e. HTTPS). @Luc’s answer contains clear explanations on why certificates are used, and on what the guarantees rely on. Most enlightening is this excerpt:

You have to trust the CA not to make certificates as they please. When organizations like Microsoft, Apple and Mozilla trust a CA though, the CA must have audits; another organization checks on them periodically to make sure everything is still running according to the rules.

So the whole system relies on big companies checking on each other. Some of the trusted CA are governmental (from various governments) but the most often used are private business (e.g. Thawte, Verisign…). An important point to make is that it suffices to subvert or corrupt one CA to get a fake certificate which will be trusted worldwide; so this really is as robust as the weakest of the hundred or so trusted CA which browser vendors include by default. Nevertheless, it works quite well (attacks on CA are rare).

Note that since the certificate parts are quite isolated in the protocol itself (the certificates are just opaque blobs), SSL/TLS can be used without certificate validation in setups where the client “just knows” the server’s public key. This happens a lot in closed environments, such as embedded systems which talk to a mother server. Also, there are a few certificate-less cipher suites, such as the ones which use SRP.

This brings us to the second foundation of SSL: its intricate usage of cryptographic algorithms. Asymmetric encryption (RSA) or key exchange (Diffie-Hellman, or an elliptic curve variant), symmetric encryption with stream or block ciphers, hashing, message authentication codes (HMAC)… the whole paraphernalia is there. Assembling all these primitives into a coherent and secure protocol is not easy at all, and the history of SSL is a rather lengthy sequence of attacks and fixes. My second answer gives details on some of them. What must be remembered is that SSL is state of the art: every attack which has ever been conceived has been tried on SSL, because it is a high-value target. SSL got a lot of exposure, and its survival is testimony to its strength. Sure, it was occasionally harmed, but it was always salvaged. It is rather telling that the recent crop of attacks from Duong and Rizzo (ASP.NET padding oracles, BEAST, CRIME) are actually old attacks which Duong and Rizzo applied; their merit is not in inventing them (they didn’t) but in showing how practical they can be in a Web context (and masterfully did they show it).

From all of this we can list the reasons which make SSL work:

  • The binding between the alleged public key and the intended server is addressed. Granted, it is done with X.509 certificates, which have been designed by the Adversary to drive implementors crazy; but at least the problem is dealt with upfront.
  • The encryption system includes checked integrity, with a decent primitive (HMAC). The encryption uses CBC mode for block ciphers and the MAC is included in the MAC-then-encrypt way: both characteristics are suboptimal, and security with these choices requires special care in the specification (the need of random unpredictible IV, basis of the BEAST attack, fixed in TLS 1.1) and in the implementation (information leak through the padding, used in padding oracle attacks, fixed when Microsoft finally consented to notice the warning which was raised by Vaudenay in 2002).
  • All internal key expansion and checksum tasks are done with a specific function (called “the PRF”) which builds on standard primitives (HMAC with cryptographic hash functions).
  • The client and the server send random values, which are included in all PRF invocations, and protect against replay attacks.
  • The handshake ends with a couple of checksums, which are covered by the encryption+MAC layer, and the checksums are computed over all of the handshake messages (and this is important in defeating a lot of nasty things that an active attacker could otherwise do).
  • Algorithm agility. The cryptographic algorithms (cipher suites) and other features (protocol version, compression) are negotiated between the client and server, which allows for a smooth and gradual transition. This is how current browsers and servers can use AES encryption, which was defined in 2001, several years after SSLv3. It also facilitates recovery from attacks on some features, which can be deactivated on the client and/or the server (e.g. compression, which is used in CRIME).

All these characteristics contribute to the strength of SSL.

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QotW #36: How does the zero-day Internet Explorer vulnerability discovered in September 2012 work?

2012-09-28 by roryalsop. 0 comments

Community member Iszi nominated this week’s question, which asks for an explanation of the issue from the perspective of a developer/engineer: What is exactly being exploited and why does it work?

Polynomial provided the following detailed, technical answer:

CVE-2012-4969, aka the latest IE 0-day, is a based on a use-after-free bug in IE’s rendering engine. A use-after-free occurs when a dynamically allocated block of memory is used after it has been disposed of (i.e. freed). Such a bug can be exploited by creating a situation where an internal structure contains pointers to sensitive memory locations (e.g. the stack or executable heap blocks) in a way that causes the program to copy shellcode into an executable area.

In this case, the problem is with the CMshtmlEd::Exec function in mshtml.dll. The CMshtmlEd object is freed unexpectedly, then the Exec method is called on it after the free operation.

First, I’d like to cover some theory. If you already know how use-after-free works, then feel free to skip ahead.

At a low level, a class can be equated to a memory region that contains its state (e.g. fields, properties, internal variables, etc) and a set of functions that operate on it. The functions actually take a “hidden” parameter, which points to the memory region that contains the instance state.

For example (excuse my terrible pseudo-C++):

class Account
 int balance = 0;
 int transactionCount = 0;
void Account::AddBalance(int amount)
 balance += amount;
void Account::SubtractBalance(int amount)
 balance -= amount;
The above can actually be represented as the following:
private struct Account
 int balance = 0;
 int transactionCount = 0;
public void* Account_Create()
 Account* account = (Account)malloc(sizeof(Account));
 account->balance = 0;
 account->transactionCount = 0;
 return (void)account;
public void Account_Destroy(void* instance)
public void Account_AddBalance(void* instance, int amount)
 ((Account)instance)->balance += amount;
public void Account_SubtractBalance(void* instance, int amount)
 ((Account)instance)->balance -= amount;
public int Account_GetBalance(void* instance)
 return ((Account)instance)->balance;
public int Account_GetTransactionCount(void instance)
 return ((Account*)instance)->transactionCount;
I’m using void* to demonstrate the opaque nature of the reference, but that’s not really important. The point is that we don’t want anyone to be able to alter the Account struct manually, otherwise they could add money arbitrarily, or modify the balance without increasing the transaction counter.

Now, imagine we do something like this:

 // ...void* myAccount = Account_Create();
Account_AddBalance(myAccount, 100);
Account_SubtractBalance(myAccount, 75);
// ...
 if(Account_GetBalance(myAccount) > 1000) // <-- !!! use after free !!!
Now, by the time we reach Account_GetBalance, the pointer value in myAccount actually points to memory that is in an indeterminate state. Now, imagine we can do the following:

  1. Trigger the call to Account_Destroy reliably.
  2. Execute any operation after Account_Destroy but before Account_GetBalance that allows us to allocate a reasonable amount of memory, with contents of our choosing.

Usually, these calls are triggered in different places, so it’s not too difficult to achieve this. Now, here’s what happens:

  1. Account_Create allocates an 8-byte block of memory (4 bytes for each field) and returns a pointer to it. This pointer is now stored in the myAccount variable.
  2. Account_Destroy frees the memory. The myAccount variable still points to the same memory address.
  3. We trigger our memory allocation, containing repeating blocks of 39 05 00 00 01 00 00 00. This pattern correlates to balance = 1337 and transactionCount = 1. Since the old memory block is now marked as free, it is very likely that the memory manager will write our new memory over the old memory block.
  4. Account_GetBalance is called, expecting to point to an Account struct. In actuality, it points to our overwritten memory block, resulting in our balance actually being 1337, so the loan is approved!

This is all a simplification, of course, and real classes create rather more obtuse and complex code. The point is that a class instance is really just a pointer to a block of data, and class methods are just the same as any other function, but they “silently” accept a pointer to the instance as a parameter.

This principle can be extended to control values on the stack, which in turn causes program execution to be modified. Usually, the goal is to drop shellcode on the stack, then overwrite a return address such that it now points to a jmp esp instruction, which then runs the shellcode.

This trick works on non-DEP machines, but when DEP is enabled it prevents execution of the stack. Instead, the shellcode must be designed using Return-Oriented Programming (ROP), which uses small blocks of legitimate code from the application and its modules to perform an API call, in order to bypass DEP.

Anyway, I’m going off-topic a bit, so let’s get into the juicy details of CVE-2012-4969!

In the wild, the payload was dropped via a packed Flash file, designed to exploit the Java vulnerability and the new IE bug in one go. There’s also been some interesting analysis of it by AlienVault.

The metasploit module says the following:

> This module exploits a vulnerability found in Microsoft Internet Explorer (MSIE). When rendering an HTML page, the CMshtmlEd object gets deleted in an unexpected manner, but the same memory is reused again later in the CMshtmlEd::Exec() function, leading to a use-after-free condition.

There’s also an interesting blog post about the bug, albeit in rather poor English – I believe the author is Chinese. Anyway, the blog post goes into some detail:

> When the execCommand function of IE execute a command event, will allocated the corresponding CMshtmlEd object by AddCommandTarget function, and then call mshtml@CMshtmlEd::Exec() function execution. But, after the execCommand function to add the corresponding event, will immediately trigger and call the corresponding event function. Through the document.write("L") function to rewrite html in the corresponding event function be called. Thereby lead IE call CHTMLEditor::DeleteCommandTarget to release the original applied object of CMshtmlEd, and then cause triggered the used-after-free vulnerability when behind execute the msheml!CMshtmlEd::Exec() function.

Let’s see if we can parse that into something a little more readable:

  1. An event is applied to an element in the document.
  2. The event executes, via execCommand, which allocates a CMshtmlEd object via the AddCommandTarget function.
  3. The target event uses document.write to modify the page.
  4. The event is no longer needed, so the CMshtmlEd object is freed via CHTMLEditor::DeleteCommandTarget.
  5. execCommand later calls CMshtmlEd::Exec() on that object, after it has been freed.

Part of the code at the crash site looks like this:

637d464e 8b07 mov eax,dword ptr [edi]
 637d4650 57 push edi
 637d4651 ff5008 call dword ptr [eax+8]
The use-after-free allows the attacker to control the value of edi, which can be modified to point at memory that the attacker controls. Let’s say that we can insert arbitrary code into memory at 01234f00, via a memory allocation. We populate the data as follows:
01234f00: 01234f08
 01234f04: 41414141
 01234f08: 01234f0a
 01234f0a: c3c3c3c3 // int3 breakpoint
1. We set edi to 01234f00, via the use-after-free bug. 2. mov eax,dword ptr [edi] results in eax being populated with the memory at the address in edi, i.e. 01234f00. 3. push edi pushes 01234f00 to the stack. 4. call dword ptr [eax+8] takes eax (which is 01234f00) and adds 8 to it, giving us 01234f08. It then dereferences that memory address, giving us 01234f0a. Finally, it calls 01234f0a. 5. The data at 01234f0a is treated as an instruction. c3 translates to an int3, which causes the debugger to raise a breakpoint. We’ve executed code!

This allows us to control eip, so we can modify program flow to our own shellcode, or to a ROP chain.

Please keep in mind that the above is just an example, and in reality there are many other challenges in exploiting this bug. It’s a pretty standard use-after-free, but the nature of JavaScript makes for some interesting timing and heap-spraying tricks, and DEP forces us to use ROP to gain an executable memory block.

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QotW #35: Dealing with excessive “Carding” attempts

2012-09-14 by scottpack. 0 comments

Community moderator Jeff Ferland nominated this week’s question: Dealing with excessive “Carding” attempts.

I found this to be an interesting question for two reasons,

  1. It turned the classic password brute force on its head by applying it to credit cards
  2. It attracted the attention from a large number of relatively new users

Jeff Ferland postulated that the website was too helpful with its error codes and recommended returning the same “Transaction Failed” message no matter the error.

User w.c suggested using some kind of additional verification like a CAPTCHA. Also mentioned was the notion of instituting time delays for multiple successive CAPTCHA or transaction failures.

A slightly different tack was discussed by GdD. Instead of suggesting specific mitigations, GdD pointed out the inevitability of the attackers adapting to whatever protections are put in place. The recommendation was to make sure that you keep adapting in turn and force the attackers into your cat and mouse game.

Ajacian81 felt that the attacker’s purpose may not be finding valid numbers at all and instead be performing a payment processing denial of service. The suggested fix was to randomize the name of the input fields in an effort to prevent scripting the site.

John Deters described a company that had previously had the same problem. They completely transferred the problem to their processor by having them automatically decline all charges below a certain threshold. He also pointed out that the FBI may be interested in the situation and should be notified. This, of course, depends on USA jurisdiction.

Both ddyer and Winston Ewert suggested different ways of instituting artificial delays into the processing. Winston discussed outright delaying all transactions while ddyer discussed automated detection of “suspicious” transactions and blocking further transactions from that host for some time period.

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QOTW #33 – Communications infrastructure after a nuclear explosion

2012-08-24 by Polynomial. 3 comments

A few weeks ago, I was sat pondering nuclear bombs. To any of you who frequent the DMZ, this shouldn’t be much of a surprise, as it’s pretty much par-for-the-course for my imagination on a Wednesday night. I started thinking about the electromagnetic pulse released from a nuclear explosion, and how it might affect electronic devices. “But surely,” I thought, “a nuclear bomb would negate any interesting post-blast resilience implications by turning all local electronic devices into glowing dust!”. How wrong I was.

After a bit of research, I came across High-Altitude Nuclear Explosions (HANE). No, this isn’t the title of the latest Michael Bay movie, but rather the concept of detonating a nuclear bomb at an altitude greater than 30km. Whilst this might sound rather ridiculous, certain countries have actually done it. In the early 60s, the USA and Russia performed a series of HANE tests, in order to better understand the potential for anti-satellite weaponry. These tests showed that the electromagnetic pulse and ensuing radioactive fallout was capable of destroying or damaging satellites in space rather indiscriminately. The tests caused numerous satellites to fail after a short period of time, due to severe radiation damage. What’s really interesting about HANE, though, is that the explosion releases a giant electromagnetic pulse, without the hassle of re-enacting that dream scene from Terminator 2 where Sarah Connor’s skeleton is left clinging onto a chain-link fence.

To quote the Wikipedia article:

This high-altitude EMP occurs between 30 and 50 kilometers (18 and 31 miles) above the Earth’s surface. The potential as an anti-satellite weapon became apparent in August 1958 during Hardtack Teak (a HANE test). The EMP observed at the Apia Observatory at Samoa was four times more powerful than any created by solar storms, while in July 1962 the Starfish Prime test damaged electronics in Honolulu and New Zealand (approximately 1,300 kilometers away), fused 300 street lights on Oahu (Hawaii), set off about 100 burglar alarms, and caused the failure of a microwave repeating station on Kauai, which cut off the sturdy telephone system from the other Hawaiian islands.

That’s one hell of an electromagnetic pulse!

After I’d got over the initial excitement of learning that it is actually theoretically possible to sizzle microchips from space using nukes, I decided to post a question on Security SE. In short, I wanted to know how worldwide communications infrastructure, especially the Internet, was protected from such attacks. This is where our resident nuclear weapons “enthusiast” Thomas Pornin came in, with a wonderfully detailed answer.

It turns out that the Internet is, like a condom machine in the Vatican, amazingly redundant. Obviously not quite the same kind of redundant, but redundant nonetheless. If a network link goes down, packets are routed through other links. It’s a self-healing network. This means that you would have to knock out multiple inter-continental network links in order to cause severe disruption. Furthermore, it has plenty of redundant channels that are likely to still function after a large EMP:

An interesting issue with radio and satellite communication is temporary disturbance of the ionosphere. The electromagnetic pulse would cause electrons to be jiggled about in the upper atmosphere, creating areas of increased and decreased electron density. A lot of long-range radio communication relies on “bouncing” radio waves off of the ionosphere, which means that such communications are likely to suffer strong interference. Longer wavelength signals are likely to be disrupted more than short wavelength (GHz) signals, due to some interesting physics wizardry I won’t go into.

Of course, in the case of a real war, we’d have to worry about anti-satellite weapons knocking out communications too. Thankfully though, under-sea cables are shielded by a big blanket of water, which absorbs electromagnetic radiation. This is why submarines send up a radio mast or buoy. The good news is that our fastest and most reliable network links will actually end up being our most resilient, because they’re on the sea bed. Furthermore, optical fiber cable is not affected by electromagnetic induction, like copper wiring is. So, if all hell does break loose, the phat-pipes should still be able to serve you your daily dose of StackExchange! Yay!

But not everything relies on hardware interlinks. We also have to take into account the systems that facilitate the core functionality of the internet. An interesting example of this is DNS. There are thirteen root nameservers that facilitate the absolute top tier of DNS functionality. Without the root name servers, we wouldn’t be able to reliably translate domain names into IP addresses. Think of them as a set of mirrors for a global directory, where top-level domains (TLDs) are indexed. These entries point to other DNS servers, which point to other DNS servers, etc. We’re left with a large hierarchical map of DNS resolution. Now, whilst thirteen servers sounds rather flimsy, the actual number of servers involved is much larger. A neat technique called anycast allows multiple physical servers across the world to represent a single root name server. This is not the same as cloud computing, which is often touted as a panacea for uptime-critical solutions. Guess what? The cloud is not redundant! But I digress. In order to take down the entire DNS system, you’d need to nuke Japan, England, France, Germany, most of eastern Europe and the entire east and west coasts of America into oblivion. At that point, I don’t think the remaining radiation-resistant insects would be particularly interested in whether the DNS system is functioning or not.

The biggest threat HANE poses to our infrastructure is to our power grid. The world is coated with a mesh of power wiring, stretching over hundreds of miles of land. Since the cables are so long, and are very likely to cut through the magnetic lines of flux in a perpendicular manner, the induced currents could be massive. Local substations would burn out, street lighting would fry, circuit breakers would pop, and fuses would blow. Without power, our worries about communications infrastructure being disrupted would be rather pointless. The servers that host anything worth accessing would be down anyway, and it’d be likely that you couldn’t boot your PC or charge your laptop, due to lack of power. Even when sections of the power grid come back online, the demand would be massive, causing further outages and brown-outs.

So, how can we protect ourselves? Here’s a few ideas:

  • Wrap everything important in a giant Faraday cage. Not exactly practical for power plants or datacenters, though.
  • Ensure that significant chunks of the world’s communications infrastructure is built around trans-oceanic cables and optical links.
  • Ensure that nation-critical services are distributed globally, with the ability to self-heal if remote systems become unreachable.
  • Be prepared to switch to lo-tech communications in the event of such a disaster.

Perhaps the thing to take away from this analysis is that nukes are dangerous, and there’s not much you can do to prevent their aftermath. The best policy is to not detonate nukes at high altitude, or if possible, not to detonate nukes at all.

Nukes are bad, m’kay.

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QOTW #32 – How can mini-computers (like Raspberry Pi) be applied to IT security?

2012-08-06 by Terry Chia. 0 comments

This week’s question is nominated by me: How can mini-computers (like Raspberry Pi) be applied to IT security?

There are 2 parts to the question.

1) What practical applications such mini-computers have in IT security, or what role they could play in cyber-defense, network analysis, etc.

2) What risks might they introduce to a local network environment that should be considered?

The top rated answer by Tobias, suggest that mini computers like the Raspberry Pi could be used as cheap penetration testing tools, linking to the Pwnpi distribution, a specialized linux distro for the Raspberry Pi. The answer also links to the Pwnplug, a small compact penetration testing drop box that has a full suite of penetration testing tools.

The answer by Rofls reinforces the answer by Tobius, stating the mini-computers like the Raspberry Pi could be used as cheap, disposable hardware for hacking when coupled with a USB Wireless Adapter. The hacker would only lose a small amount of money if the Raspberry Pi was discovered.

The answer by Diarmaid links to IPFire, which can turn the Raspberry Pi into a cheap.firewall or IDS/IPS.

adamo also suggest that the Pi can be used to build cheap sensor networks to monitor Wifi, Ethernet or Bluetooth. He also suggest that the Pi can be used as emergency DHCP or DNS servers in situations where a quick fix is needed.

The Raspberry Pi is an example of a growing class of cheap hardware that can be used for hacking and penetration testing purposes. HakShop has a great set of cheap hardware that can perform task that used to require dedicated equipment costing thousands of dollars. This makes the threat of hacking even more prevalent as more users are able to afford the hardware needed to perform specialised task.

This is clearly going to present a new and interesting challenge for security professionals to defend against. I look forward to seeing what solutions the many bright minds in this industry can come out with.

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