Blackboard (in)Security

The University recently recently paid for a vulnerability assessment and penetration test, which came back saying that, apart from a few minor things, everything was fine and secure. I take issue with this finding for several reasons, most of which I won't go into here. Now, I haven't actually seen the report produced by the company, but I have had verbal reports from the IT technicians that 'nothing serious' was found.

The University uses a hateful product called Blackboard as a Virtual Learning Management System. This is a web-based application allowing access to learning materials, grades, etc., from anywhere in the world. The problem is that it doesn't use an encrypted connection and uses a simple Session ID cookie to assert that you are an authenticated user. There are two problems with this. Firstly, if I capture your cookie and send it with my HTTP request, then I will be treated as you and can see or do anything as you. Secondly, and much more importantly, is that the username and password are sent in plaintext!

I shouldn't have to explain why this is such a bad idea, but I can't understand why this wasn't picked up as a major security hole. A simple packet sniffer will pick up anyone's username and password, giving full access to the network and other services, such as email, home directories, etc. The trouble is that it's not just students who login to this service, all the academics and admin staff do as well. You can imagine what could be done by grabbing a lecturer's username and password.

How easy is it to actually launch a sniffing attack? Well, surprisingly easy (unless you are a pen tester, in which case it won't surprise you at all). Consider the fact that people do connect to this service from public wireless hotspots or from shared networks, such as the halls of residence or the university network itself. It isn't difficult for someone to sniff the network and extract the user's password. 'MAJOR SECURITY WEAKNESS' not 'nothing serious'.

I advise people to connect to Blackboard instances via SSL connections at the very least. It doesn't stop all the attacks, but it will stop simple packet sniffing.

Secret Sharing Algorithm for Protecting Files in the Cloud

Data stored in the cloud can be compromised or lost (see my previous post). So, we have to come up with a way to secure those files. We can encrypt them before storing them in the cloud, which sorts out the disclosure aspects. However, what if the data is lost due to some catastrophe befalling the cloud service provider? We could store it on more than one cloud service and encrypt it before we send it off. Each of them will have the same file. What if we use an insecure, easily guessable password to protect the file, or the same one to protect all files? I have often thought that secret sharing algorithms could be employed to good effect in these circumstances instead.

What are secret sharing algorithms? They are algorithms that will share a secret between several parties, such that none of them can know the secret without the help of others. Either all or a subset of them will need to get together and put their parts together to obtain the original secret. A simplistic solution can be achieved by XORing the secret with a random number, then giving the result to one party and the random number to the other. Neither one can find out what the secret was without the other. To retrieve the secret they only need to XOR the two parts together again. This can be extended to any number of parties.

A more sophisticated way would be to allow the secret to be retrieved from a subset of the parts distributed. In the previous example, if any of the parties loses their part, or refuses to disclose it, then nobody can reveal the secret. This isn't much good if one of our cloud service providers fails. On the other hand, if we can share the secret between three people, but only require any two to regenerate the original, then we have some redundancy. This is an example of a (k,n) threshold scheme with k=2 and n=3.

How do we achieve this though? Well, Adi Shamir proposed a simple secure secret sharing algorithm. It is based on drawing graphs. To uniquely define a straight line, you need two points on that line. Similarly, to define a parabola you need three points. A cubic requires four, etc. So, we can distribute points on a line to each party we want to share the secret with. The order of the line will determine how many of them need to get together to regenerate it. So, we could define a random straight line and distribute three points on it to three different parties. However, only two of them need to get together to regenerate the original secret.

We set up a (k,n) threshold scheme by setting the free coefficient to be the secret and then choosing random numbers for each of the other coefficients. The polynomial then becomes the following:


where a₀ is our secret. Now we can distribute points on the line to each of the n parties simply by calculating y for a series of different values for x. We can use the Lagrange Basis Polynomials to reconstruct the equation of the line from k points. However, we do not need to reconstruct the whole line, we are only interested in the free term. This simplifies the equations that we need to use. For example, if we have a straight line, then we only need two points (x₀,y₀) and (x₁,y₁). We can then calculate a₀ as follows:
Similarly, for a parabola and three points (x₀,y₀), (x₁,y₁) and (x₂,y₂) we have:
This should be fairly simple to implement and use. You would need to sign up to a few cloud services, but you wouldn't have all your eggs in one basket and you wouldn't be reliant on weak passwords.

PhoneFactor Security

I was asked recently to look at the security of the PhoneFactor 2-factor authentication solution. If you don't know what it is, then you can find out more here, but essentially you enter your username and password, then they phone you on your pre-defined number and press the # key to validate the authentication. The problem with just pressing the # key is obvious, but they allow you to configure entering a PIN number rather than just pressing the # key. To my mind, there should be no other option than having to type in the PIN number. However, this isn't necessarily a brilliant idea. As I've said before in this blog, a lot of phones log the digits dialled, in which case that PIN isn't secure.

I was also told that the PSTN and GSM networks are secure, so this is a good solution. I'm not sure I agree that PSTN and GSM networks have good security. Analogue PSTN is easy to listen in to with proximity and GSM can theoretically be cracked, and probably will be within 6 to 12 months. So that PIN number isn't really secure. Plus there is the cloned SIM card problem as well.

http://www.mobileindustryreview.com/2009/08/gsm-encryption-can-be-cracked-for-500.html

Having said that, PhoneFactor looks quite good as you enter the PIN on the phone line, not the login dialogue. The problem that Bruce Schneier has referred to is that of a Man-in-the-Middle attack. Most 2-factor authentication methods are susceptible to a MITM attack, including RSA tokens and other hardware tokens. Basically, if I set up a website, for example, to mimic your corporate portal, then you will enter all your details into my page, including your one-time pass code. I will forward them on to the real portal and do whatever I like logged in as you.

The one advantage is that I have to intercept every login attempt, and wait for you to login before I can gain access. Without a 2-factor system, once I've read your username/password combination I can login whenever I like. PhoneFactor would appear to mitigate some of this risk by doing the authentication out of band. However, there is still an attack vector for a MITM attack. In the same way as before, you login to my portal, I forward your credentials, PhoneFactor phone you and you put in your PIN, they enable my session! Obviously, there are other attack vectors as well.

Another potential issue is that you are charged for the phone calls made by PhoneFactor on your behalf. These can be significant costs. In the UK calls to landlines are free, but am I always at my desk when I want to log in? No, I'd want it on my mobile; that will cost me $0.23 per login (East Timor $3.25). So, I could rack up the bill for you company by getting them to call through to someone. If I do this enough times (especially if that person is on holiday in another country with higher charges) I can use up all your credit and none of your users can login.

There is a privacy issue as well. PhoneFactor will know every time you log in or access your bank, etc. How do they protect that data? Do you want them to know that information, even if you do trust they won't accidentally disclose it?

However, I am not against 2-factor authentication. Indeed I think it is a good thing, as users will choose poor passwords, reuse them everywhere and write them down. Similarly, they will give them away to phishing scams. 2-factor authentication removes all of those problems, but by no means is it absolutely secure. PhoneFactor seems OK, but it's not particularly cheap or phenomenally secure. There are some other good software solutions that are pretty cheap as well, and that can combat shoulder-surfing when entering PIN numbers, etc. There are a couple of examples on a blog post I did a couple of months ago: http://blog.rlr-uk.com/2009/06/user-friendly-multi-factor.html

The bottom line is that they are more secure than username/password, but none of them are absolutely secure against all attacks.

Security Questions for your Cloud Services Provider

Comodo Vision Video Blog

Cloud Services or Cloud Computing are getting a lot of attention in IT circles, promising cost-effectiveness, flexibility, and time-to-market advantages over traditional alternatives. However, they also increase your security risk by expanding your security perimeter to include that of your service provider. This video blog poses some key questions to ask your Cloud services/Cloud Computing provider regarding data security as well as advice to reduce the risk to your business introduced by Cloud Computing.

See my third video blog for Comodo Vision here.

APWG Report 1st Half 2009

On 27th September the APWG released their First Half 2009 Phishing Trends Report. This provides some interesting/worrying reading. Most notably is the rise and rise of rogue anti-malware programs.

Rogue anti-malware programs are programs that run on a user's machine and falsely identify malware infections. They then inform users that the malware can be removed by purchasing their anti-malware program. The installed software, in many cases, does absolutely nothing. The malware author has made their money off the user and doesn't care about them or the fact that their machine is left vulnerable to other malware. However, there is another breed of rogue anti-malware that will install other malware onto the user's machine, often adding them to botnets or adding trojans and spyware. According to Panda Labs' Luis Corrons, rogue anti-malware programs are proliferating with "exponential growth. In the first quarter of 2009 alone, more new strains were created than in all of 2008. The second quarter painted an even bleaker picture, with the emergence of four times as many samples as in all of 2008."

Most of these rogue anti-malware programs have a common root - they even look the same. So how come they aren't detected as malware? Well, often they employ server-side obfuscation so that each version is slightly different, thus defeating some signature-based scans. Also, you have to remember that many of these don't perform any malicious actions and, therefore, don't trigger other alarms.

What can we do about rogue anti-malware? Well, simply don't trust anything on the Web saying that you are infected or that they will scan you for free. Do not install any anti-malware from a company that you do not know and always check for validity of links and downloads. There are many companies out there providing free basic anti-malware or sophisticated products for a relatively low price that are legitimate, such as: Panda Security, AVG, Comodo, Symantec, etc. If you do get infected by one of these programs then you need to remove it. Instructions for removing the most common ones can be found at http://www.anti-malware-blog.com/ - N.B. be warned that I have not assessed or validated their instructions and there is no guarantee that they won't cause other problems.

What about the rest of the report? Well, phishing is still on the increase, with reported phishing highs for the first half of the year exceeding those of last year significantly (about 7%). 21,856,361 computers were scanned to determine host infection rates. 11,937,944 were found to be infected (54%), which is an increase of over 66% from the last quarter of 2008. Banking trojan/password stealing crimeware infections rose by more than 186%. Finally, payment services have taken the top spot in the most targeted industry sector from the financial sector, although this is still a close second. To see how this compares, a previous blog post of mine on this shows how things have changed.

For more information about the Anti-Phishing Working Group, to report phishing attacks or to see their reports yourself, visit http://apwg.org/

Telephone and Fax Services Security

In this day of doing everything online, we still rely heavily on services delivered over POTS (Plain Old Telephone Service). Banks and credit card companies still require the telephone to make certain changes, queries and security checks, even though most functions can be performed online. Medical records, bank details, security key order requests, etc., are routinely transferred by facsimile. However, are these secure? Are they more or less secure than doing the same thing online?

I'm not going to talk about the underlying security of POTS, but concentrate on a couple of easy attack vectors on the end device of the user that I have recently observed. A couple of weeks ago, I needed to amend something on one of my credit card accounts (I would tell you which bank, only it's my personal credit card and I don't want phisers knowing which banks I have accounts with). This bank has an automated telephone answering system to make things more efficient and reduce staff required - pretty standard. So I made sure that I was in a room on my own, to prevent eavesdropping my conversation, and dialled the number. The automated system asked me to type in my full credit card number on the keypad.

The problem with doing this is that the telephone will remember these digits as part of the last number dialled. Therefore, all someone would have to do is to recall the last number dialled and read off the credit card number. If they actually dial it they would be put through as the legitimate card holder. Now, admittedly they will probably ask some security questions on the other end before making any changes, but these may consist of simply asking for a date of birth, which is fairly easy to find out. Even if you don't know this information, other information may be given away in the mean time (e.g. who the card holder is as they normally use your name in any greeting). The problem is compounded if you make a call from work, where you will probably be using an exchange. Exchanges will store all the numbers dialled, including any options or credit card numbers entered on the phone's keypad. This log can simply be printed out and your details read off. Of course the number dialled will show which bank you are using as well, although this can also be gleaned from the first 6 digits of your credit card number.

Things can potentially get worse if you use facsimile or fax machines. There are different types of fax machines that work in different ways. Most will keep a log of calls and faxes sent and received. This may or may not be a problem, depending on the level of detail of the log and whether you're typing in credit card details during a phone call made on the machine. However, some fax machines use rolls of pigment on acetate (or similar) to print the fax out when received. The problem here is that these rolls are wound through during printing and that part is never reused (otherwise you will get gaps in your printing). However, what this means is that when you come to throw the roll away once used, it will have a perfect facsimile of everything printed on the machine since the roll was put in, only in negative. To get round this, you must shred, or otherwise destroy, the used roll, not just throw it in the bin.


As to whether this is more or less secure than an online transaction is a difficult question to answer. On the one hand, you often need physical access to the phone or fax machine to get to the logs, although telephone exchanges are often online. Also, sifting through a bin outside a premises isn't that hard and can often be very rewarding. On the other hand, transactions online are encrypted and people are more aware of the security implications in general. However, malware and man-in-the-middle attacks can still thwart this type of transaction, but it does require more skills than sifting through a bin.

Not all data leakage comes from computers, pen drives, etc. Sometimes a seemingly innocuous device can betray your information and breach your security. Unfortunately, you have to think of all possible attack vectors and mitigate the risks. This is why a full information policy that covers all forms of data is required.

Human Factors in Information Security - Errors & Violations

Human failures are often described as Slips, Lapses, Mistakes and Violations. These are grouped into two categories: Errors and Violations. The difference here is the intent - violations result from conscious decisions to disregard policies and procedures, whereas errors have no malicious intent. Also, violations often involve more than one form of misconduct, whereas errors are often isolated.

Don Turnblade has stated that in his experience "well trained staff had a 3.75% unintentional non-compliance rate; they did not realize that installed software compromised data security. About 0.4% of end users were intentionally non-compliant, generally willful persons with strong technical skill or organizational authority who were unaccustomed to complying with computing restrictions."

So what are the different types of error? Dealing with each in turn, we have Slips, Lapses and Mistakes.

• Slips - actions not carried out as intended, e.g. pressing the wrong key by accident. Slips usually occur at the task execution stage.
• Lapses - missed actions or omissions, e.g. forgetting to log out, or a step in a configuration process.
• Mistakes - occur due to an incorrect intention, whilst believing it to be correct, i.e. they are deliberate actions with no malicious intent, e.g. misconfiguration of a firewall. Mistakes usually occur at the planning stage.

So who causes the error or violation and how do we combat them? Slips and Lapses are usually the fault of the user, but can be mitigated by making it more difficult for the user to make the error, e.g. by having confirmation dialogs for slips and better training for lapses. Mistakes tend to be the fault of designers and are slightly more difficult to combat as designer education is required or outside technical expertise needs to be brought in. However, this doesn't always solve the problem if they don't have the skills and knowledge required. Finally, violations can often be laid at the door of the managers. It is often the case that a culture of violations is accepted by senior management, who fail to impose proper sanctions or take the threat seriously.

All of these have to be dealt with to have a secure system and most of it boils down to having proper user education and training in place.