posted by Igor Ljubuncic on Mon 2nd Apr 2012 15:41 UTC
IconYou have just bought tickets to an exotic vacation spot. You board the flight, you land safely, you pull your netbook from your backpack, fire it up, and then check if there are any available Wireless networks. Indeed there are, unencrypted, passwordless, waiting for you. So you connect to the most convenient hotspot and start surfing. Being addicted as you are, you want to login into your email or social network just to check if something cardinal happened in the world during your four-hour flight. You're about to hit the sign in button. Stop. What you're about to do might not be safe.

This super-dramatic introduction is supposed to highlight today's topic: How to stay safe on the road. And I'm not implying anything you may do in your person, like getting robbed or kidnapped or drinking local tap water, but rather the security involving your electronic gadgets and your online habits. Because if you bring your computer with you, you will want to connect it to the outside world. And this is where troubles begin. Or not. Hopefully, the article will highlight all the perils and pitfalls of unsafe hex and how you can avoid them.

What's all this fearmongering?

There's none really. But you have probably read a million articles and scare posts telling you how this or that person's email credentials or credit card details where stolen. You will hear a lot of warnings about not connecting to insecure networks. You will be warned about using public hotspots and Internet cafes.

All right, let's try to analyze the situation one byte [sic] at a time.

First of all, it all comes down to trust. In a nutshell, you trust your own computing device and you trust your ISP, at the very least. This means the chain of communication at home is safe. Once you leave that cushty enclave, things change.

There are several layers of potential dangers that might compromise the security, privacy and integrity of your online activities outside your home. We will start with the bottom layer.


Whenever your computer connects to a new network, it tries to obtain an IP address. In most cases, your computer's network device will be configured to use DHCP, so it will broadcast a request for an address. The available DHCP server on your network will respond, a short exchange of information will occur, and you will become a member of the network.

At this point, your machine will become a visible node in the local network. This means that other clients will be able to communicate with you. They might ping you or try to connect to available services running on your machine. And here's the interesting part. If your machine has running services configured to listen on external networks and accept unauthenticated requests, you may inadvertently compromise your data. Moreover, if you are running outdated versions of programs with known and easily exploitable vulnerabilities, it may also be possible for determined and skilled attackers, if present on your network, to try to gain elevated privileges through the exploit and become administrative users on your machine.

Examples that highlight these possibilities include sharing of drives via Samba, being logged in as root/admin and running an ancient, buggy version of a P2P client, having SSH with a trivial 123456 for password, and more. How do you go about protecting against network problems?

The simplest solution: firewall.

Firewall setup

This is the easiest way of ensuring your operating system is inaccessible by other peers on your network. By default, the firewall will block all incoming connections to your ports, unless you specifically create exclusion rules. And you're done.

Now, advanced users may want to try to minimize the exposure vector of their machines, regardless of the firewall. This means disabling unneeded services, like turning off file and printer sharing when traveling or not using BitTorrent at the airport, and running as a user with limited privileges, so even if there are problems, they will be minimal.

A good example would be Ubuntu - it comes with no services listening on external networks, so the firewall is not even necessary, and you work as a normal user without root privileges.


We're still talking about network, but one level higher. DNS stands for Domain Name System, a protocol designed to translate domain names, like websites, into IP addresses. For example, when you enter into the address bar of a browser, your DNS server, most likely the one provided by your ISP and automatically configured for you, will translate the query into an IP address. There will be a long chain of packets being sent back and forth, but eventually, you will end up reading the content as you expected, without knowing anything about any numbers.

Whenever you connect to a network, you're assigned a DNS server. You can check this by examining your network information. In Windows, for instance, open the command prompt and type ipconfig /all. In Linux, take a look at /etc/resolv.conf. The IP addresses will change based on what network you connect to.

If you want to use only specific, trusted DNS server, then you will want to use static DNS servers that are not overriden by DHCP assignments, by this requires changing some configuration files on your machine. More importantly, this means having IP addresses of known and trusted DNS servers available. Worldwide public services include Google Public DNS and Open DNS, but whether you want or trust them is a different story altogether.

Assuming you go with the default option, you will be relying on whatever DNS server is assigned to you for name to IP address translation. In theory, a rogue server could malform your requests and return bogus information. So what do you do?

There are several things you can do. First, normal web browsing. Connecting to non-secure websites, the ones you normally see prefixed with http://, unless you're using one of the modern, fancy browsers that hide the information from you, you will not know if you're being forwarded to bogus sites or not. Or rather, not without some extra work, but then, you don't need this article.

But just browsing is not really important. Things become interesting when you need to input your username and password into a login field, or better yet, provide your credit card details.

My recommendations is not to login into non-secure sites when connected to untrusted networks outside your home. This probably extends to your social network, so you might be hard tempted. We will discuss that later on.

For secure websites, the ones starting with https://, things are a little different. Secure connections are all about creating an encrypted tunnel between your browser and the remote server so that anyone sniffing the exchange of information will see meaningless, random packets rather than streams of clear text containing private data. But there's a catch. How do you know you're connected to the site you think you're connected to?

This is the reason why secure connections are always accompanied with certificates. Connecting to an HTTPS site is not enough; you also need to be sure that the site is what it claims to be. To that end, the idea of worldwide-trusted Certificate Authorities (CA) was created, with the sole pupose of issuing identification cards to websites. When you connect to a site, it offers its certificate. Your browser compares the certificate to its own list. If the two match, you proceed to login. If not, you are warned that you are connecting to an untrusted site.

Untrusted site certificate warning

Now, the word untrusted does not imply bad or malicious. It merely means that your brwoser does not know whether the site is what it claims to be. There are two potential reasons. One, it has a certificate that differs from the one it is supposed to have. Two, it has a self-signed certificate.

Domain name mismatch

In this situation, you need to make the decision whether to trust the site or not. For most people, the best choice is to stop and consult an expert. However, there are several ways common users might help themselves distinguish between true and bogus sites.

One of the best ways of doing this is to keep bookmarks of important sites. This way, there's less of a chance of being offered a wrong site when you search for it. Moreover, if your bookmarked sites are trusted but have self-signed certificates, then you should write down the site's certificate checksum, so that when you connect from an untrusted network, you can compare the certificate presented to you with your saved list. In theory, it is possible to forge certificate fingerprints to match those of genuine sites, but this is extremely unlikely.

Website fingerprint

Another way of keeping track of certificates is a handy Firefox extension called Perspectives. This extension uses several online databases, known as notaries, to compare the current site's fingerprint with results taken in the last 30 days. If the fingerprint appears unchanged, you may assume that the site is ok, despite the warning. If the certificate seems to be different or has changed many times recently, you might assume that you're possibly connecting to a wrong site. This should help you decide whether to proceed.

Perspectives addon

Therefore, when you go about surfing somewhere outside your home, like the restaurant or the airport Wi-Fi spot, you will know with a very good degree of confidence whether you can connect to the sites you need. This also extends to providing your credit card details and other sensitive information. As long as your machine is your own, it has a firewall, and the Web connections are secure and trusted, you're all right.

Secure connectivity

There are other ways you can connect safely to your sites, including non-encrypted ones. This can be done by using tunneling. Your current device becomes a viewing terminal, and all your confidential activities happen on a trusted remote machine. For example, you may connect to your home box using SSH. Of course, this implies being able to connect to your home box, but we will discuss that shortly.

There are several methods you can use to establish secure remote connections. Indeed, one of these is SSH. Encrypted VNC sessions are another possibility. You can also use a Virtual Private Network (VPN) service like OpenVPN. However, all of these solutions require a somewhat higher technical knowledge.

To be able to achieve this, you will require a second machine in a secure location, like your home or office, up and running. It must also be accessible from outside, which means using a static, externally routable IP address or maybe Dynamic DNS (DNS). It also requires opening ports in your home network firewall, either the router or the box itself, with all the additional security precautions. Your ISP must also allow that kind of remote connectivity. Next, we come down to configuring the remote sharing services properly, including robust passwords, limited connection attempts, non-standard ports, and other settings.

OpenVPN setup


Now we come to your personal data. Having a firewall will prevent external access, but what if your laptop, netbook or smartphone gets stolen? There's always a possibility someone might steal your gadgets, but when traveling, the risk increases. To that end, you might want to considering keeping your data inside encrypted containers on your disk, or even encrypting the entire hard disk. For most people, having a file container inside which the data is kept is sufficient in most cases. The simplest way you can configure encrypted file containers is using a program like TrueCrypt.

You may also want to consider moving your user profile or home directory into the encrypted container, so that application settings, browser links, saved passwords, and possibly other sensitive data are also not available if the gadget gets compromised. This method makes work a little more complicated, and there's the risk of a permanent data loss if the encrypted container gets deleted or corrupted, but it outweighs the dangers and risks of damage in the case of theft. Naturally, you should have multiple backups of your data in safe, trusted locations, but this is true regardless of your travel plans. You can learn more about TrueCrypt in this tutorial.

TrueCrypt container setup

Using a computer other than your own

All of the above only applies to your personal computing devices. And none of these apply if you must use a public computer. In that case, all bets are off. You have no way of knowing whether your activities are recorded or logged in any way, even if you appear to be savvy and can examine various settings to try to determine if keyloggers, network sniffers or other tools might be active.

My recommendation is to refrain from providing any personal information on public computers, including seemingly innocent logins into forums and social network, especially if they are not encrypted. The recommendation also extends to not plugging in your removable devices, like digital camera smart cards, USB thumb drives, external disks, and other gadgets into these public computers. It's more than just viruses and whatnot, and frankly, these are overrated. It's the simple fact of making your data accessible on machines other than your own. If you do not trust the machine, then simply don't use it.

Best travel option

Now, let's see what your optimal traveling computing set should look like.

Ideally, you would want to use a Linux-based operating system for your travel machine. Normally, almost all efforts to compromise your machine will be focused on Windows, so you will gain by just being different. Moreover, Linux is easier to secure out of the box, because of its least-privilege principle, allowing you to work as a limited user with no ill side effects.

You will have your browser with several important, secure sites bookmarked, and a list of sites' fingerprints saved in a text file for comparison in the case of discrepancies, or alternatively, run Firefox with Perspectives. You will also keep an encrypted container for your data, and possibly the entire home directory. You will be running a firewall to make sure there are no ports left open by mistake.

Asus eeePC running Ubuntu Netbook Remix

Last but not the least: YOU

No technology in the world can protect you from yourself. There's nothing that can stop you from divulging important personal data in web forms, chat rooms, forums, social networks, and other sites. If you decide you want to install software, share fires or input your private information somewhere online, then firewall, encryption and all other solutions become meaningless.

The safety of your digital travel starts with the concept of discipline. If you cannot adhere to that, then you will have a hard time ensuring the integrity and privacy of your data. But if you are willing to follow simple principles, firewall, secure connections and data encryption will cover some 80-90% of your needs.


Travel security seems complicated, but it narrows down to a small number of protection layers - firewall for basic network filtering, secure sites control against rogue redirection and misidentification, data encryption, and basic discipline. Everything else comes secondary.

Hopefully, this article clears away some of the fear mist that shrouded your mind. It is all too easy to get lost in the media panic generated around the risks and perils of travel, as if you're going to Mordor on your own. But things are much simpler. There you go.


About the author:
Igor Ljubuncic aka Dedoimedo is the guy behind He makes a living out of his very hobby - Linux, and holds a bunch of certifications that make a nice pile in the bottom drawer.

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