13 Nov, 2017

Public Computers and Malware

Learn how to protect yourself from malware when using public computers, and how to keep your personal information safe from hackers and cybercriminals.
Name seven places where you might find public computers. Let me see if I can guess what you came up with. Hotels, libraries, airports, coffee shops, job search assistance locations, schools, and conference facilities. Let me add one more; the microphone.

Let's begin with the realization that some public computers are open to all or mostly all of the public, but even those that have restrictions on who can use them are still public computers. Hotel computers are typically only available for hotel guests to use. Computers in libraries are normally accessible to anyone. Public computers at airports are generally found after airport security which limits the access the public has to them. Typically the public computers at airports are only found in the executive lounges, which places further restrictions on the number of people who can access them. Job search assistance computers may be available to everyone or only to people who are using the company's services. School computers may be available for teachers to use, students in the classroom to use, and in some cases in classrooms where the general public can take computer courses. Usually, computers in conference centers are not likely to be any more dangerous than public computers in other settings but at some conferences the danger is a certainty. The risk at the Black Hat conference is such that IT departments mandate that employees are forbidden to use the conference computers and are encouraged to avoid the ATM machines in and near the hotels too.

And now we get to the microphone. At many conferences, the presenters use their own laptops, however at some conferences the presenters use a shared computer. Many years ago I was speaking at a security conference that had a shared computer. Before my presentation, the audio/video technician copied my presentation from my thumb drive to the presentation computer and then returned my thumb drive to me. After several months I finally pulled out my thumb drive and put it on my laptop. Instantly my antivirus software brought up a warning that the Mariposa virus had been detected. Although physical access to the presentation computer was restricted, data from multiple unknown private sources was being shared. in many ways this is no different than sharing a thumb drive with a friend or coworker, but I want you to be aware of the computers we might use that we might not think of as being public computers.

In a blog titled "What Comes to the Business Center Computer Stays on the Business Center Computer" I explained the data risks associated with business center computers. In the blog, I promised to address the malware threat in my blog here this week. The most well-known threat from malware on public computers is, of course, the keystroke logger. If you login to any account requiring a password while using a public computer there is always the threat that your credentials have been compromised. This is what keeps your corporate security team awake at night - worrying about employees logging into compromised computers. Keystroke loggers are not the only malicious software threat. As I explained in the example above, worms can spread through USB Devices. Macro viruses are also a threat, and we have seen a resurgence of them. If you create a document on a computer that has been infected with a macro virus your new document may be infected before you of type a single word. If you email the document or just copy it to your thumb drive to share later, you will be spreading malware.

There is some good news. Hotels have begun providing more secure public computers for their guest's use. Kiosk interfaces restrict users to a small set of activities thereby reducing most malware and data compromise risks. Restricted user rights and application whitelisting prevent the installation of both unauthorized good as well as malicious applications. Some hotels require guests to login to a session. Even though no password is required, when the guest logs off, all of the data from the prior session is deleted. On some hotel computers, users can access the file system however they do not have administrator privileges and are restricted to writing to or copying from specific locations. All other locations are inaccessible, even for viewing.

I rarely use public computers other than those at hotels and occasionally airline lounges. However, I still recommend that you do not use public computers for anything that requires you to log in or to access or create sensitive data. Limit your use of these machines to browsing the web, playing solitaire, or watching cat videos and you should be safe.
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