IPICS 2010 Network Security Slides

My slides on Network Security and Steganography, presented at the Intensive Programme on Information and Communication Security (IPICS) 2010 can be downloaded below. The topics covered under Network Security are: Access COntrol Devices, Firewalls, Network Protection, Network Authentication Protocols, TLS, VPNs & Remote Access. The Steganography slides cover examples of: Image, Network, HTTP and Twitter Steganography.

A PDF of the Network Security slides can be downloaded from here.

A PDF of the Steganography slides can be downloaded from here.

Telephone Systems a Hackable Backdoor?

I have been talking to a company that provides telephone exchanges and services to companies this week on behalf of a client and it has highlighted a worrying backdoor. It turns out that many of these companies have a way to remotely connect to their exchange for support purposes - they can remotely control, configure and troubleshoot your system to get you back up and running. Exchanges often have additional modems in them to allow for remote connections. This is all very well and good from a managed service point of view, but what about the rest of your network? Can this be exploited to gain entry to your network? Quite possibly in some cases - it certainly needs to be included in your security audit and perimeter testing.

Talking about a specific company now, they supply the software to monitor and bill phone calls through the exchange. They remotely install, monitor and manage this software. How do they do that? Well, it turns out that they install LogMeIn on your machine. Now this will make outbound connections through the firewall to make the internal machine accessible from the outside world. Hang on; you're making my networked machine that controls my exchange and billing accessible by anyone? By default LogMeIn will use simple username/password type authentication.

The user who accesses the computer has to set up their account with LogMeIn and will use the same username and password combination on all machines as far as I can see. Does the company have a universal account that they use to remotely access the machines or does each user have their own? If the company uses one default username/password, then what happens if someone gets hold of that information or someone leaves? Does the password get changed? If everyone has their own account, then are they removed when they leave the company? As this is all done through the Web, they could still gain access if they aren't specifically removed from the user group.

How much do you trust all the employees of that external company? How much do you trust the disgruntled ex-employee from them who has access? It might not be that they are trying to attack you, but they may be careless about the credentials or not revoke them properly. Also, consider the case where all the internal employees of an organisation are required to have 2-factor authentication and remote access is locked down. What's the point? There is a simple username/password entry point into the network that bypasses all the secure remote access services you may have in place. How secure are the passwords that the external company use? Would they match up to your complexity requirements? If they are simple, easily guessed or shared, then they open full administrative control over a machine on your 'secure' internal network. Who patches the machine and who updates LogMeIn?

How about installing a keylogger in such a firm to pick up on their username/password combinations so that you can gain full access to every customer's network. Once on the internal machine, malware can easily be installed and attacks launched on other internal machines unhindered. How many organisations have followed best practice and installed a UTM firewall in the core of their network to segregate their servers, etc., from other internal machines? Would a machine running this software be on a normal user subnet or on the management subnet anyway? Do many SMEs have more than one subnet anyway?

Needless to say, my advice was to avoid installing LogMeIn on the machine and temporarily allow a more controlled access to the machine with a temporary account, all of which can be disabled immediately after remote installation is completed. This opens up the problem of how to obtain support, but access can be temporarily granted and then removed when support is required with relatively little effort.

Clearly any such system needs to be well documented and be part of the security audit. I would advise that companies also ask for security audit and policy information from any external company who has any kind of access to the network - this should be standard procedure.

Cisco TACACS+ Password Length

I have recently come up against a problem with using the 'new' wireless network at work. We are using Cisco kit and TACACS+ to interface onto Microsoft's AD in the back end. Technically, usernames should be able to be up to 31 bytes long (not a problem there) and the password up to 254 bytes. However, the web portal implementation that we are running has a problem with my password. It would appear that passwords of up to 16 characters are fine, but passwords in excess of 16 characters don't work.

We are currently investigating this, as it seems like a real problem, especially as we are recommending that people switch to using longer pass phrases, in excess of 16 characters. Hopefully vendors will catch up with this soon, as many still have problems with so-called 'special characters' such as punctuation and other common symbols.

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.

Personal Mobile Devices Violate Compliance

Computer Weekly recently conducted a survey via Twitter on how many organisations allow their users access to corporate email from their own private phone. Unfortunately, I haven't seen any results from this survey as yet, but it made me think about organisations that do allow private devices to attach to the network, not just mobile phones. I have also had many comments on my blog post entitled 'Mobile Device Data Breaches', which have fed into this post.

In one of those comments, someone pointed out that in their experience users are often a weak link. Isn’t it always the case that users are the weakest link? A poorly educated/trained user can compromise the best security. Unfortunately, I have seen so many organisations that do not adequately train their users or make them aware that there are policies, let alone what they mean to their daily usage of the corporate systems. I have also come across one organisation where a top executive had all the system passwords stored, unencrypted, on his PDA. He didn’t see a problem with this as he always carried it with him!

How many organisations these days have push email onto a mobile? How many of those organisations send sensitive documents around via email? Do they have encryption and password access on those devices? Not many that I’ve seen. The typical Blackberry users that I see have no password or PIN access to their phone, but it does have full access to the corporate mail exchange. These devices also have the ability to store, and even sync, corporate documents. What policies do you have to cover them?

Quoting from ISO-27002:2005 11.7.1: A formal policy should be implemented, and appropriate security measures adopted, for mobile computing and communications activities. Controls should apply to laptop, notebook, and palmtop computers; mobile phones and "smart" phone-PDAs; and portable storage devices and media. Controls include requirements for:

• physical protection;
• data storage minimization;
• access controls;
• cryptographic techniques;
• data backups;
• anti-virus and other protective software;
• operating system and other software updating;
• secure communication (e.g., VPN) for remote access; and
• sanitization prior to transfer or disposal.

The problem is that most organisations do not have adequate policies covering mobile devices. Moving away from mobile phones, are you allowed to plug a USB device into your corporate machine? Many of these devices can store sensitive data and even access the Internet themselves. What about an insecure iPhone connecting to the Internet and leaking data? Most organisations aren't even aware that you can lock down USB usage via tools, but policies should definitely be in place. Alan Goode, from Goode Intelligence, said the following:

"I feel that you can lock down with security policy and tools but this is a complex problem as the combination of mobility and technology diversity, e.g. I can use my iPhone to connect to the enterprise network and store sensitive data on it, is creating a major headache for infosec professionals. As well as the problem with laptops and USB drives we are also seeing a growing use of employee-owned mobile devices, netbooks, games consoles, smart phones, all having IP and WiFi capabilities and all capable of picking up enterprise data and email."

There are a number of things we can do to stop these devices from compromising the network by blocking their use. We can block USB devices from being able to connect unless they are a managed resource, so that users can't just plug anything they bring in from home. All USB devices have an ID, which can be registered with a central authentication server to check before a computer allows it to be used. Of course this needs third-party software, but can be done quite easily. We can also block devices from being able to obtain an IP address or connect to the corporate network in the first place. We shouldn't have a free-for-all attitude on the network. It should be locked down to approved devices only. Only managed devices can connect and they will have to authenticate.

I think it’s asking for trouble to allow users to connect their own private devices to the network or services. I don’t see how you can comply with any standards or your own security policies when allowing this, as you don’t know what’s connected or how it’s configured. Even if they are secure (a very big IF), by not knowing the configuration or being able to audit it, you are surely in violation of any accreditation or certification that you may have because you cannot test or 'prove' your compliance.

Should an Administrator Trust their Users?

The answer is yes and no (note, in this blog, I'm not talking about cryptographic or identity trust, but systems trust). There are two aspects to this. Firstly, do you think your users will deliberately act against your organisation or try to harm the system? This is not usually the case for corporate employees - you also have severe sanctions available if they do. The second aspect is, do you trust your users NOT to make mistakes? Everyone makes mistakes; we're only human. You don't want accidental updates or changes, so in this sense maybe you shouldn't trust your users.

Actually there are three overall approaches to system trust on networks. We can trust all of the people all of the time (bad idea, but much more common than you'd think), trust no one at any time (maybe too excessive and hinder functionality), or we can trust some of the people some of the time. The last one is usually the best strategy to adopt for your network.

Finally, we have to decide on the overall approach to security. Are we permissive or restrictive? In a permissive environment you can do everything, apart from those things on a blacklist. In a restrictive environment, you can do nothing, apart from those things on a whitelist. From a security standpoint restrictive is better, but from a usability standpoint permissive is better. If you can manage the whitelist successfully, this is the better solution and only trust some of the users some of the time.

ATM & Bank Card Security

I recently read an article in New Scientist entitled "Want to clone bank cards? Just press 'print'". They state that it has been discovered that

"... a devious piece of criminal coding that has been quietly at work in a clutch of cash machines at banks in Russia and Ukraine. It allows a gang member to walk up to an ATM, insert a "trigger" card, and use the machine's printer to produce a list of all the debit card numbers used that day, including their start and expiry dates - and their PINs. Everything needed, in fact, to clone those cards and start emptying bank accounts."

This is possible because ATM Terminal vendors have succumbed to financial pressures, and the demand for greater functionality, and moved to using standard modular PC architectures and off-the-shelf operating systems, such as Microsoft Windows and Linux. These ATM devices then become vulnerable to similar malware as their desktop counterparts.

SpiderLabs, part of Trustwave, identified that in this case a new version of the 50KB lsass.exe Windows XP file is loaded onto the system via a compromised Borland Delphi installer utility, isadmin.exe (note, that's LSASS.EXE, not 1SASS.EXE as some have reported). You can view the full report from Trustwave as a PDF here. The legitimate lsass.exe executable is used to cache session data in Windows, so that users don't have to re-enter passwords when receiving new emails or returning to a website, which is essentially what the malware developers want to do with the card data. Actually, this has no place on an ATM, but may not be picked up, due to the fact that it is, by default, on most Windows XP installs.

If a trigger card is not detected, the malware stores the transaction data to a file called tr12 and key or PIN data to a file called k1 in the C:/WINDOWS directory. If a trigger card is detected, then a menu of 10 options is displayed for 10 seconds, with functions including: uninstalling, deleting logs, printing logs via the built-in printer encrypted with DES and possibly the ability to export the data onto the trigger card. This particular malware only works on transactions in US dollars, Russian Rouble or Ukrainian Hryvnia. It is also said that chip-and-PIN cards across Europe are not vulnerable to this malware as the PIN is encrypted in the secure PIN pad.

It has been speculated that deploying the malware was either an inside job or the result of bribes and threats; the reasoning being that an attacker would have to have physical access to the ATM to deploy the malware. However, the ATMs and banking network, although separate from the Internet, have not necessarily been hardened enough. Back on 25th November 2003 the first known case of a worm (Welchia) infecting Windows XP based ATM machines was reported, which used the closed financial network to propagate. This was possible because the ATMs weren't patched by the financial institutions in question. This brings on the whole problem of patch management on ATMs as well as placing greater restrictions on the financial networks. How long will it be before keyloggers are available for chip-and-PIN cards as well?

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.