File Deletion versus Secure Wiping (and how do I wipe an SSD?)

When is a deleted file actually removed from your device, or at least when does it become unrecoverable? It turns out that this question isn't always easy to answer, nor is a secure file deletion easy to achieve in all circumstances.

To better understand this we have to start from the basic principle that when you delete a file on your computer you are only deleting the pointer to the file, not the actual data. The data on your hard disk drive (HDD) is stored magnetically in sectors on platters that spin round inside the HDD (we'll come onto SSDs in a bit). So, how does the computer know where to look for your file? It has a table of indexes such as the File Allocation Table (FAT) or Master File Table (MFT) in NTFS. When you delete a file in your OS, all you are actually doing is removing its entries from the table of indexes so your OS can't find it any more and doesn't know it's there. However, all the data is still stored on the disk and IS STILL RECOVERABLE! Tools like Piriform's Recuva can scan your disk for orphaned files and file fragments and allow you to recover them.

So, how do you actually securely delete a file so that it is unrecoverable? The most common way to securely delete a file is to overwrite it one or more times with other data before removing the entries in the index table. Different schemes for overwriting the data exist from NIST, the US DoD, HMG, Australian Government, etc. These usually consist of 1-3 rounds of writing all zeros, all ones or random patterns to the sectors, i.e. physically overwriting the data on the disk before 'deleting' it. There are many tools available to securely delete files and securely wipe drives according to these requirements.

Excellent, we've solved the problem of secure file deletion. Or have we? Well, no. There are usually some hidden areas of drives such as bad sectors that haven't actually failed, Host Protected Area (HPA), Device Configuration Overlay (DCO), etc. Interestingly, with DCO it is possible that you have a significantly bigger HDD capacity than is reported by the drive. Some manufacturers will sell bigger HDDs with the capacity artificially reduced for a variety of reasons. However, the important point here is that there are areas of the drive that you cannot normally access, but that may contain remnants of your data.

What of Solid State Drives (SSD)? Are they easier or harder to securely wipe? It turns out that they are much harder to wipe. SSDs can store your data anywhere and the controllers are programmed to 'wear' the drive evenly by keeping track of areas that get a lot of use and moving data around on the drive. So, assuming you keep roughly the same file size, when you edit your file on an HDD the original physical sectors will usually get overwritten with the new version. However, with SSDs, it is likely that the new version will be written to new areas of the disk, leaving the originals intact. It is very difficult to know where an SSD actually writes your data. They also have many hidden areas as above as well as capacity used to cope with failing sectors or evening up the wear. The long and tall of it is that if you use software to overwrite the file, like you would on an HDD, you probably haven't overwritten the data at all, but you will have reduced the life of your drive.

So how do we secure delete a file on an SSD? There aren't that many manufacturers of SSDs and most of them provide utilities to securely wipe their drives using the ATA Secure Erase (SE) command, which is a firmware supported command to securely wipe the whole drive, releasing electrons from the storage cells, thus wiping the storage. That's just wiped our whole drive though; how do I wipe just a file? Well, you can't really. You either wipe the drive or don't bother.

There is a 'gotcha' here as well though. I said earlier that there aren't many SSD manufacturers, but if you go to buy one there seem to be loads. Well, people like HP and IBM rebrand other people's SSDs (I believe they use Crucial). What's the harm in this? Well, they will sometimes re-flash the firmware to have their own feature set. That means that the original manufacturer's Secure Erase software may not work on them and the IBMs and HPs don't always provide an alternative (other than the traditional overwriting you would do on an HDD).

There must be something you can do though, surely? Well, yes there is. If you first encrypt your drive, or use file-level encryption, then the data that is on the drive should be unrecoverable (assuming you haven't stored the keys on the drive as well). This is actually your best bet for an SSD, but also does no harm on a traditional HDD.

OK, so if I want to get rid of a drive that is End of Life, what should I do? If it's an HDD, you should secure wipe it by overwriting the whole drive several times as described above, degauss it (i.e. using electro magnets to wipe the magnetic data on the platters) and then shred the drive. Yes, I did say shred the drive... into tiny pieces. You can get some impressive machinery to do this, or use a service to shred them on site for you. What about SSDs? Use the ATA Secure Erase function from the manufacturer's software and then shred them as before (just make sure the shredding process actually destroys the chips so they can't be re-floated onto another board to read them).

eBay's Weak Security Architecture

Well eBay are in the news due to their breach of 145 million users' account details. There are a few worrying things about this breach, beyond the breach itself, that point to architectural issues in eBay's security.

The first issue is that a spokeswoman (according to Reuters) claimed "that it used 'sophisticated', proprietary hashing and salting technology to protect the passwords." This sounds very much like security through obscurity, which doesn't work. So, either they are using a proprietary implementation of a publicly known algorithm, or they have created their own. Both of these situations are doomed. As always, no one person can think of all the attacks on an algorithm, which is why we have public scrutiny. Even the best cryptographers in the world can't create new algorithms with acceptable levels of security every time. Do eBay have the best cryptographers in the world working for them? I don't believe so, but I could be wrong.

Also, if their argument is that hackers don't know the algorithm so can't attack it, then I'm fairly sure they're wrong there too. Even if the algorithm was secure enough to stand up to analysis of the hashes only, as hackers have eBay staff passwords perhaps they also have access to the code! If, on the other hand, they have their own implementation of a public algorithm I have to question why? Many examples are available of implementations that have gone wrong and introduced vulnerabilities, e.g. Heartbleed in OpenSSL. Do they think they know better?

The second issue is that they don't seem to encrypt Personally Identifiable Information (PII). This is obviously an issue if a breach should occur, but, admittedly, doesn't solve all problems as vulnerabilities in the web application could still expose the data. However, it is likely to have helped in this situation.

Finally, and most importantly, how did gaining access to eBay staff accounts give attackers access to the data? Database administrators shouldn't have access to read the data in the databases they manage. Why would they need it? Also, I would hope that there are VPNs between the corporate and production systems with 2-factor authentication. So how did they get in? Well, either eBay don't use this standard simple layer of protection, they leave their machines logged into the VPN for extended periods or they protect the VPN with the same password as their account.

Even if eBay do implement VPNs properly with 2-factor authentication, the production servers shouldn't have accounts on them that map to user accounts on the corporate network. Administrative accounts on production servers should have proper audited account control with single use passwords. Administrators should have to 'sign out' an account and be issued with a one-time password for it by the security group responsible for Identity and Access Management (IAM).

All this leads me to think that eBay have implemented a weak security architecture. 

Web Hosting Security Policy & Guidelines

I have seen so many websites hosted and developed insecurely that I have often thought I should write a guide of sorts for those wanting to commission a new website. Now I have have actually been asked to develop a web hosting security policy and a set of guidelines to give to project managers for dissemination to developers and hosting providers. So, I thought I would share some of my advice here.

Before I do, though, I have to answer why we need this policy in the first place? There are many types of attack on websites, but these can be broadly categorised as follows: Denial of Service (DoS), Defacement and Data Breaches/Information Stealing. Data breaches and defacements hurt businesses' reputations and customer confidence as well as having direct financial impacts.

But surely any hosting provider or solution developer will have these standards in place, yes? Well, in my experience the answer is no. It is true that they are mostly common sense and most providers will conform to many of my recommendations, but I have yet to find one that, by default, conforms to them all.

Site Categorisation

There are several different categories of hosting and several different ways to categorise sites, with different requirements. However, in my opinion, sites should be categorised based on the information that they contain and the level of interaction allowed. Sites should then be logically and physically separated into their categories.

Sites can be categorised as brochure sites if they have static content or do not collect information. These sites can then further be categorised into public or private depending on whether the data that they contain is public or not. Sites within these categories may be co-hosted with other sites in the same category, but the two categories should be segregated.

Sites can be classed as data collection apps if they collect sensitive or personally identifiable information (PII) from the user. Sites within this category should be hosted on their own servers with no co-hosting and be segregated from all other sites. The data must be stored on separate segregated database servers that are secured and firewalled off.

Finally, any site with even more sensitive data on it or company secrets should be hosted internally if you have the expertise in house.

Hosted Environment

The following list is an example of the requirements for secure web hosting. It is not necessarily complete, but if you do not have the following then you may have issues in the future. All websites and web applications must:

• be hosted on a dedicated environment - the hosting machine may be virtual or physical, but must not be shared with any 3rd parties. Multiple websites and applications from the same company may be hosted on the same machines according to the categories above
• have DDoS protection in place
• have AV running and configured properly on the server along with appropriate responses and reporting
• be hosted behind a Web Application Firewall (WAF) to protect against common attacks, plus allow the ability to configure it for specific services
• be hosted on security hardened Operating Systems (OS) and services to an agreed build standard
• be subject to regular and timely patching of the OS and services
• be subject to regular security testing and patching of any Content Management System (CMS) in a timely manner if used
• be subject to active monitoring and logging by the provider for security breaches and reporting to/from the organisation
• have formal incident management processes for both identifying and responding to incidents
• not be co-hosted with additional public services beyond HTTP/HTTPS (e.g. no public FTP)
• not allow DNS Zone Transfers
• use proper public verified SSL certificates - with a preference for Extended Validation (EV) certificates
• ensure that management services and ports are on different IP addresses and domain names preferably, but must not be available through the normal login or visible on the website
• ensure that administrative interfaces and services are restricted to certain IP addresses at least, but make use of client-side certificates or two factor authentication (2FA) if possible
• ensure staging servers are available for test and development, which must not be shared with live sites and should be securely wiped at the end of testing as soon as the site is deployed live
• ensure staging and test environments are not available on the public Internet or, if there is no alternative, they must be devoid of branding and sensitive information in all ways and restricted as above
• be built on a tiered architecture, or at least the database (DB) server must not sit on the same server as the web front end, must not be accessible from the Internet and must be securely segregated from the front end
• use encrypted storage for all sensitive information, (e.g. passwords and sensitive information)

Hosting Services

It is up to the hosting provider and third party developers, but should be backed up by specific contractual clauses, to ensure that:

• the site is backed up regularly off site in a secure location using encrypted media where the keys are stored separately from the media and able to be restored in a reasonable time frame with a suitable rotation and retention policy
• hardware and media that has reached the end of its life is securely destroyed
• all sites are made available for pentesting prior to going live and at regular intervals
• all vulnerabilities considered of medium risk and above should be remediated prior to go-live
• all sites are available for on-going regular automated Vulnerability Assessments
• domain names, code and SSL certificates are registered to the company and not a third party
• there are agreed processes for identifying approved personnel to authorise changes
• change management processes that track all changes are in place along with rollback and test plans
• capacity and bandwidth are actively managed and monitored
• all management actions are accountable (unique accounts allocated to individuals)
• all management should be through secure ingress from trusted locations
• egress filtering should be in place to block all non-legitimate traffic

Encrypted ZIP Archives Leak Information

This post is just a quick note to remind people who use encrypted ZIP archives to store or transfer confidential information, that the headers of the archive are not encrypted. Therefore, the filenames, dates and sizes of all the files within the archive can be read by anyone, without the key. Is this a problem?

Well, I believe it is. Many people and organisations have naming conventions for files. How do you know which report to open if the filename doesn't give you some clue? Often filenames will include project names or codes, departments and even the names of the people writing the report. Would you give this information out to anyone walking down the street? I have seen targeted Spear Phishing attacks on users whereby emails have been sent with what look like project spreadsheets attached with the correct naming conventions and project codes. These attacks were very convincing for an unsuspecting user. Filenames can leak enough data to start launching social engineering attacks and to concentrate cracking effort on the correct files.

What can you do? Either don't use encrypted ZIP archives to send sensitive data, or rename every single file to random names before adding them to the encrypted archive (remember that you should really do this to all files every time you want to add anything to an encrypted archive, even if the filename doesn't reveal anything as otherwise you will again be potentially advertising the really sensitive files).

Flaw in email security means signed mails cannot be encrypted

I was at a company the other day that uses a well-known email encryption solution as they have some very sensitive information that they need to send both internally and externally. As is common for these solutions, it is possible to automatically sign the email by putting a keyword in the subject line, such as 'signemail'. Similarly, the mail will be encrypted automatically if the confidential flag is set or a keyword, such as 'encryptemail' is added to the subject.

So far, so good. There are no messy button presses or extra steps for the user. However, there is a flaw with the solution. (I should point out that at this moment it is unclear if it is a product problem or a configuration problem, hence my not mentioning the product.)

The issue is that the signing the message appears to take precedence over encryption. So, if you add both keywords to the subject then the message will only be signed and not encrypted. Now the encryption solution does also sign the message, so if you want it encrypted then you don't need to specifically sign it as well.

So is this really a problem or am I just making a fuss? Well, I can envisage several situations when it would be a problem. The most likely is probably replying to a signed message with confidential data. Let's say that Alice puts in a request for sensitive information from Bob via a signed email - only certain people can have access to the information so it is reasonable to expect Alice to digitally sign the request, but the request is not sensitive in itself.

Now, if Bob replies to that request with the sensitive information attached he will follow policy and mark it as confidential and add the encryption keyword, 'encryptemail', to the subject line. He will now assume that the information will automatically be encrypted. However, if he doesn't remove Alice's 'signemail' keyword it will just be signed and not encrypted. This then violates the policy and sends confidential information in plaintext while the user believes that it has been encrypted.

It also highlights that you shouldn't use a keyword that might be used as part of everyday language. For example, don't use the keyword 'sign' as someone could send a sensitive document with a subject something like 'Contract for you to sign'.

I suggest that everyone using this type of solution should test it to see if this happens on their system. If it does, you will, at the least, need to publish an advisory warning to your users.

Base64 Encoding is NOT Cryptography

I have once again come across an IT department who were/are firmly convinced that the commercial web application that they use is secure and has encrypted user details. What it actually does is Base64 encode the password. This is not encryption and must be treated as plaintext.

So what is Base64 encoding and why do we have it? Well, a large number of popular application layer protocols are ASCII text based, i.e. they transfer plain text over the network. A good example of this is HTTP - the protocol used to transfer HTML (or Web) pages around. Originally, only text pages were sent with markup embedded to style it. However, soon other resources were added to the web including pictures, documents, etc. HTTP is designed to transfer plain ASCII text, so how do you transfer a JPEG photograph? Answer: You convert it into plain ASCII text.

The basic principle of converting a file into text is to use the data to represent an index to the ASCII character, e.g. 'A' is 63, 'B' is 64, 'a' is 97, '8' is 56, etc. So, if the first four bytes of your file are 63, 64, 97 and 56, this can be represented by 'ABa8' without loss. However, ASCII is actually only 7 bits and we usually use 8-bit bytes (because of IBM setting the standard - actually a byte was historically just the number of bits required to store a character). Also, ASCII character 13 is a carriage return, 27 is escape and 8 is backspace. These are non-printable and, worse than that, could corrupt the communications as well as remove other characters. So, we can't just do a straight conversion from bytes to ASCII.

This is where Base64 conversion comes in. We split the file up into 6-bit 'bytes', rather than 8-bit. 6 bits give us 64 possible values. These are then represented by the digits, upper and lowercase letters and a couple of symbols ensuring that they are always printable and don't cause problems. So, the Base64 encoded password is just a 6-bit 'byte' representation of an 8-bit byte password and it is trivial to convert between the two. There is no security in Base64 encoding anything. Perhaps I should repeat that again.

Base64 encoding something is not encrypting it and provides NO SECURITY whatsoever!

I am constantly surprised and disappointed that people think that Base64 encoding something will protect it. I know TLS has its problems, but why aren't all web applications using it?

The little JavaScript tool below will allow you to encode and decode Base64 encoded text to see what it's like and how simple it is. If you find Base64 encoded passwords on your network via sniffing then you can use this to decode them.

Enter Text:


Select Encoding or Decoding:

Encode | Decode

True Random Numbers from Random.org

Much of security relies on randomness - encryption keys should be random and random passwords are more secure than dictionary words or predictable sequences. The problem is, how do we generate a random number?

Well, actually, this is a trick question. The answer is that you can't generate random numbers, but you can observe them. Most programming languages give you a random number generator, so why not just use that? Well, it's not actually a random number generator, but a Pseudo-Random Number Generator (PRNG), or more accurately a Pseudo-Random Sequence Generator (PRSG). Given the same seed value, it will produce the same output every time. Try seeding the random number function in your favourite programming language then run your program a few times. You should see the same numbers coming out each time.

The reason for this is the function used to produce random numbers is just a mathematical formula that takes an input and gives an output. To have a random number out, you need a random starting value. Most will seed themselves on the clock, but this isn't random; it isn't even unpredictable. A simplistic example of a PRNG, as given by Knuth in his seminal books, is as follows:

X = (a*X+c) mod m

Random number = X/m for some suitable large prime number m and fixed values a and c both less than m (indeed c is usually a small number <10).

This can be seeded by setting X to the seed value and will give the same sequence of pseudo-random numbers out, as can be seen. However, it isn't random. If I know your seed value I can recreate your sequence of numbers. If you seed it on the clock it is often possible to work out a window of opportunity and obtain a range of seed values. Admittedly, this could be large, but an exhaustive search of these would be quicker than breaking the code that relies on them in many cases. Recently, a large Linux distribution was found to have a flaw in its key-generation that introduced a major weakness into the RSA public-key codes generated on those machines. This was due to predictability of the keys and a lack of randomness.

So, what can we do? We can observe randomness in the natural world. Random.org uses background white noise as a source of randomness. This gives good randomness and distribution of numbers. They offer several options to generate random numbers, sequences or even passwords. An example of their random number service is given below. I'm not saying that they are the best option or the only option, but you must use truly random numbers in your cryptography and secure systems.

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.

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.

Mobile Device Data Breaches

Comodo Vision Video Blog

Several recent data breaches at major enterprises and governmental agencies stemmed from the loss or theft of mobile computers and USB drives. While encrypting the data on these devices isn’t a bad idea, the larger question is why was sensitive personal information stored on the mobile device in the first place?

See my first video blog for Comodo Vision here.

Wireless Network Security Recommendations

Wireless Networks are still causing businesses problems. By their very nature they are insecure, as they are a broadcast network that frequently extends beyond your physical boundary - remember radio signals don't stop at your door. There ARE security mechanisms to make them secure, but too often these are not implemented properly or are circumvented by users. It is vital that all traffic on the wireless network be encrypted, and connections authenticated, otherwise anyone with a laptop can view all your traffic. There are many mechanisms for achieving this, but at the very least you should use WPA with long pass phrases (not simple passwords) and MAC address authentication.

Don't use WEP; it can be broken easily. I won't bore you with details here, but I refer you to Google instead. However, there are several flaws such as using a linear Integrity Check Value, such that predictable bit-flipping can be used to send invalid messages that will appear to be valid. Secondly, the 40-bit shared secret is 'extended' by use of a 24-bit per-packet Initialising Vector. As any cryptographer will tell you, the more often you use the same key, the easier it is to recover the plaintext (particularly if you have known plaintext, which we do have in the headers of network packets of course). IV collisions happen surprisingly quickly, especially on corporate wireless networks, as they will usually have reasonably heavy load. TKMaxx found this out the hard way when they lost half a million credit card details to a hacker sitting in their car park. This also shows that they almost certainly didn't segregate the traffic and force it through a firewall.

So what can we do about this? Well, all modern equipment will support Wi-Fi Protected Access (WPA) and WPA2. A standard implementation of this is to use a Pre-Shared Key (PSK), i.e. a pass phrase, and the AES block cipher for encryption. This is the minimum requirement for a wireless LAN. Again, don't use simple passwords, as the security of your system is relying on them. You should use long complex pass phrases, with punctuation. Another idea is to encrypt a pass phrase using itself (or another) as a key in an encryption tool; then use the resulting base-64 encoded string as your PSK. However, automatic key negotiation and the use of digital certificates is a better option in a corporate environment (remember for wireless access you can run your own internal certificate server so that you don't incur additional costs).

This doesn't solve everything though. A little while ago the head of a department in an organisation I was involved with decided that he didn't want to have to use the docking station for his laptop as it constrained where he could work in his office. So, he didn't contact the IT department, but instead went to his local IT retailer and bought a cheap wireless access point. He plugged this into the network and, not only did he not configure any security, but he didn't even change the default password on the device. Do you categorically know that you don't have a rogue access point on your network? This can be stopped by using technologies such as 802.1X port-based authentication and a RADIUS server.

Wireless networks also need to be treated as insecure and separated from your wired network via a firewall, with real-time virus checking and an Intrusion Detection System. This doesn't mean that they have to be unprotected themselves; you should still protect them from outside attack by firewalling them off from the Internet. The important point is not to let traffic flow, unchallenged, from the wireless network onto the wired network. This is not often done though. I was in Vienna recently on business and the hotel I was staying at had free wireless access for guests. However, one night I couldn't get access and asked why. I was told that they had switched it off as someone was trying to access their servers (they weren't very proficient or experienced hackers fortunately). The point that I found more worrying was that their public wireless network was directly connected to their servers, which the hold names, addresses and payment details of guests and even the door card programming details! You can imagine what could happen if someone were to get into the servers...

Wireless networks and wired networks should not coexist on the same subnets. This is for two reasons. Firstly, it is easier to attack and, therefore, attach to a wireless network, so you don't know categorically that all stations are legitimate. Secondly, most wireless networks are used to connect mobile devices, such as laptops and netbooks, to the network. Do you know that these haven't picked up any malware whilst not connected to your corporate LAN? You can address the latter with network access control, but that's a different topic. However, all traffic from the wireless network should be treated with a level of suspicion and therefore separated. You don't have to have a separate Internet connection or new wiring to achieve this; VLANs (or Virtual LANs) can solve the problem by logically segregating the traffic into the firewall. This also allows you to provide public wireless access for visitors/customers as you can run two separate, VLANed wireless networks through the same access points onto the network - one with limited access to the corporate LAN and the other with none.

Wireless networks can be implemented securely, but remember to separate your wired and wireless networks and implement secure encryption and authentication.

The PCI DSS and Why It's Relevant to Everyone

Many of you will know that PCI DSS stands for the Payment Card Industry's Data Security Standard and most of the rest of you have probably heard of it and wondered what it was. You may immediately say I'm not interested in the Payment Card Industry and want to navigate away, but just before you do, you should know that many of the 12 recommendations are relevant to all. Actually the PCI DSS recommendations are mostly common sense that we should all be implementing anyway. I'll give a quick overview of the big 12 and how these can be applied to all networks in this blog.

According to the PCI Security Standards Council, "The core of the PCI DSS is a group of principles and accompanying requirements, around which the specific elements of the DSS are organized." The 12 recommendations that they put forward can be generalized as follows and should be adhered to by all organisations:

1. Install and maintain a firewall configuration to protect private/sensitive data
2. Do not use vendor-supplied defaults for system passwords and other security parameters
3. Protect stored data
4. Encrypt transmission of private/sensitive data across open, public networks
5. Use and regularly update anti-virus software
6. Develop and maintain secure systems and applications
7. Restrict access to private/sensitive data by business need-to-know
8. Assign a unique ID to each person with computer access
9. Restrict physical access to private/sensitive data
10. Track and monitor all access to network resources and private/sensitive data
11. Regularly test security systems and processes
12. Maintain a policy that addresses information security

Dealing with each very briefly, I’ll try to show how these can be applied to a ‘normal’ network rather than one involved in dealing with payment details. Firstly, we all know that we must have a firewall and block access from the outside world. However, just having a firewall isn’t enough, if it isn’t configured and managed properly. Every port and service open through it must be justified and have clear documentation. There must be policies and procedures in place to control the opening of ports and services through the firewall so that each one can be assessed for its impact on the overall security. Wireless networks should also be separated from wired networks by the firewall – this doesn’t mean that the wireless network has to be unsecured from the Internet or that it has no access to the wired network, just that restrictions and filtering should be in place between them. Obviously, there should be no access from outside the network into the network, as a DMZ should be set up for all public access machines. Finally, personal firewalls should be installed on all mobile machines and hardware firewalls installed at users’ home premises if external access is to be allowed.

The second should be obvious and doesn’t really need any explanation, other than to say disable as many features as you can and don’t allow any configuration or management from outside your network. There are ways to enable secure remote access to the network, thus allowing for management of servers and devices to be achieved from within the network.

The third and fourth requirements go together and mean that strong authentication is required and permissions set appropriately. However, we should also implement encryption on highly sensitive data and removable devices/mobile machines, with proper key-management processes, and Digital Rights Management (DRM) to prevent digital leakage. All data transmitted across public networks should be encrypted (whether sensitive or not).

Is there anyone who doesn’t follow point 5? You’d also think that the zyxst (6th) recommendation would be followed by all organisations, but this isn’t the case. You must have proper patch management procedures as these are critical to securing potential vulnerabilities. However, how many times do you see that the state of the server or service is lagging behind the latest patches? I have seen many commercial outfits developing web applications that are not secure as security is an afterthought and not embedded in the development cycle. This means that, even if you don’t write your own applications, you must check third party applications that you intend to use on your network. Make sure that they have been developed using secure coding guidelines and have been independently tested. An example of not taking it for granted is Apple, who has no formal security program (ref.).

The seventh recommendation sounds obvious again, but it isn’t followed even by many of those covered by the PCI DSS. Restrict access to your data by business need to know. Does your network administrator need to know everyone’s personnel details and payroll? No, so make sure they don’t have access. This is an often overlooked problem, but many organisations rely on people not looking rather than actually protecting the data. How many examples can you quote of companies, and government organisations, losing confidential data that they should never have been able to access? An example springs to mind of a large retailer that lost the names, addresses and credit card numbers of millions of customers, which were copied onto a laptop. Why would you need all this data? Presumably you want it for business intelligence purposes and data analysis. This can, and should, be delivered live through secure channels, not done from a local copy. Why do you need their credit card number though? The point is that it shouldn’t be possible to extract this data and store it on the laptop in the first place. The next two are also related to this and a previous point of requiring strong authentication, which means that you must not allow sharing of user accounts by employees (especially executives giving passwords to PAs!).

Recommendations 10 and 11 deal with monitoring and testing the network. In order to make sure that your system is functioning as expected and that your security mechanisms are appropriate and don’t have vulnerabilities, you need to monitor the network and regularly test it for vulnerabilities. Every time a significant change is made to the network, its impact on the network should be assessed and tested.

The final recommendation is to maintain an information security policy. This must cover all forms of information though, not just electronic. It should be very clear and all employees should be trained in its content and abide by the policy or face punitive measures. Employees should have to sign a copy of the security policy, stating that they have read it, understand its content and agree to abide by it. However, this has no teeth if you do not adequately train all of your employees and update them regularly on the policy and any changes.

The PCI DSS recommendations can and should be adopted by all organisations, not just those involved in payment card transactions.

Does Smart Grid Open up Covert Communications? - Smart Grid Steganography

The latest Smart Grid technology promises to reduce energy wastage and save money by enabling your household equipment to 'talk' to central servers and neighbouring equipment about their usage and energy requirements. This allows you to highlight how much equipment is costing you to run and how much you could save by turning it off, getting more efficient equipment, running it off-peak, etc. It also enables micro-generation of power and the ability to sell it to the grid or neighbouring properties. There are many privacy issues surrounding this technology, many of which are highlighted by Susan Lyon in her article 'Privacy challenges could stall smart grid'. Obviously, there are much bigger issues than the consumer part of the solution, e.g. the self-healing nature of the power grid due to failure or attack, but the fact remains that people's equipment and homes will be connected to this.

With this in mind, there is another potential issue (or advantage) in my opinion, which people are missing when they talk about security. What about if we aren't attacking the grid or trying to steal energy? Most of the security discussions are centred around being resistant to attack. What if we use the Smart Grid as another network that isn't monitored as well as other channels? We can use it as a communications channel by exploiting valid signals and spurious equipment or usage. This could be a great Steganographic channel (Steganography being the art of hiding a message in a plaintext carrier).

The privacy debate is looking at the control of the release of your information and tracking. However, I can always see what my energy usage/generation is and obtain signals from my smart equipment. I can choose to allow someone else to see this as well (even if it is by telling them what my password is). I can now increase/decrease my energy usage or generation to send coded information to another party. This can get more sophisticated by having a device that can pretend to be a number of household appliances with different energy demands and patterns. If this will transmit it's usage onto the grid, then we can also read this off the grid. Similarly, I can get two devices to communicate usage and pricing levels over the network, that's what it's for. What about if I agree to sell you energy from my micro power plant at a particular price - it could be an absurd price, it doesn't matter so long as it is a valid communication according to the protocols used. The price will be a number presumably, so what if my number is an encrypted message and not a price at all? (Could micro power generation be used for money laundering?)

The protocols to be used for a large-scale Smart Grid are still in development, but they are likely to have similar traits to current networks (indeed Cisco is pushing an IP solution). This means that Steganographic IP traffic is just as possible on this network as on the Internet. It also means that we should be able to send virtually any message we like on the network. The smart grid operators will have to check for well-formed traffic, but we can still conform to the standards and send spurious data as long as we don't attack the network. Can we use this for covert communications?

InfoSecurity Europe 2009

Well, a couple of weeks ago I went to InfoSecurity Europe 2009 at Earl's Court, as I do every year. If you've never been, but are at all interested in network and information security or are looking for vendors, then I highly recommend visiting. To my surprise, and for the first time I can remember, Microsoft wasn't there. Apart from that, however, all the usual players were there and, to be honest, it was all much the same as before. There was no new emerging technology or hot topic, just new developments of old technologies. A couple of years ago we had the hot topic of 'social engineering' and 'securing the user'; ok, we all knew that the users were our weak link and phrases like "we spend all our time securing the first 2000 miles and forget about the last 2 feet", and "our network would be totally secure, reliable and fully functional if we didn't let users login", have always been commonplace, but there were new mass threats, new education programmes and new tools at the disposal of net admins to deal with them.

However, this year was different; nothing really sprang out. OK, cloud computing and Software-as-a-Service (SaaS) has expanded and matured, but other than that we see the same products and services as before. What amazes me is how some vendors and speakers can get it so wrong and don't appear to understand the actual level of security offered or operating environment in which their products will be used. I'm not going to list actual vendors here, but how can an encryption solution for mobile users that doesn't encrypt the data at rest be viable? Encrypting network traffic is commendable, but not the only safeguard required. What if they now lose their laptop, mobile or pen drive? A secure USB pen drive vendor admitted, when questioned, that files were decrypted into the C:\Temp folder while in use, then deleted after encrypting for storage on the drive again. They couldn't tell me if this was a secure delete or a simple removal of the pointer in the file allocation table as normal. Regardless of the deletion process, however, how many applications can read and write to that folder? What's to stop me from writing a very small bit of code to monitor that folder every few seconds and take copies? This might be secure enough if it is on a corporate machine, but why not just store the file on it then and not bother with the drive?

Similarly, email security is always a problematic area, with almost no solution fitting the technology properly. The big advantage of email, and the reason we all use it, is that it is independent of firmware - i.e. it doesn't matter what hardware, OS or email app we use, it still works. Unfortunately, security was never built in to email, so every email is like sending an electronic postcard. However, I would argue that a solution that only allows you to send encrypted email within your organisation is of limited value. What about all your customers and partners? There are also still solutions that store your files on their servers and send a link to the recipient. Why trust your files to them? I asked several vendors how they deal with password transfer, only to be told that they don't. "It's up to the user how they tell the recipient what the password is," was a common reply. We know users are unreliable, why leave it to them? I had to transfer some confidential files to someone via email recently (the only transport method they would accept), only to be told that they didn't want the hassle of decrypting it, so could I send them in plaintext. Having got over that hurdle, they wouldn't give me a mobile phone number so that I could transfer the passphrase via a call or SMS (as people seem to need them written down), asking me to email it to them. I know there are technologies out there to solve these problems, but they aren't without any problems.

This is turning into a bit of a rant and I'm getting off topic, so back to InfoSec. I was pleased to see that there were some voices of caution out there about the wholesale adoption of virtualisation without considering the security implications. One that springs to mind is Steve Moyle who has produced 10 points to consider implementing on his blog here. Virtualisation is a good technology for a number of reasons, but it does bring in new security threats and it must be implemented with these in mind and secured accordingly. I do also think that cloud computing and SaaS could be very important to SMEs (Small to Medium-sized Enterprises) who don't have the in-house expertise or large budget. They can still have large enterprise-level configurability and security, without the overheads. Finally, people seem to be taking information governance and user education seriously rather than just paying lip-service to them. In all, the show was encouraging, but many vendors are not quite there yet, which only goes to highlight that the majority of organisations are not taking the new threat-landscape seriously enough and countermeasures must be lacking.