A quick & dirty guide to malware (part 2: viruses)

A dialogue screen shown by Virus:W32/Duts.A

This is the second posting in a three-part series covering common threats a user may encounter.

This series serves as a rough and ready guide, highlighting key features and trends relevant to most users.

The One That Left

Last week I spoke of Trojans, Viruses and Worms as The Big Three. I lied a bit, though. Viruses – as a distinct malware type – probably shouldn’t be on that list any more.

Viruses have always loomed large in users’ minds as the poster child of malicious programs – heck, we even call it the anti-virus industry. In the last 10 years or so however, the number of virus infections has nosedived; our Labs, which once dealt with viruses routinely, now sees a proper virus infection about once or twice a month. Today when people talk of ‘viruses’, more often than not what they’re describing is technically a trojan or a worm, and they’re using the term in a general, ‘any malware will do’ kind of way.

That’s not to say viruses are extinct; we still receive a small, if persistent, number of queries about viruses. This may be because many businesses, households and users (both in developed countries and in recently connected developing ones) still use old, out-dated, unpatched machines or programs, or haven’t yet developed a security-conscious habits.

Whatever the case, virus infections will probably still cling on to life for a weary day after, so let’s take a look at them.

Highlights of a virus

Definition of a virus given by Merriam-Webster online dictionary

The Merriam-Webster online dictionary’s bare-bones definition of a computer virus touches on important elements most users should know, so I’ll just elaborate a bit more on some key concepts:

“usually hidden within another seemingly innocuous program”

Last week I compared a virus to a parasite, because not only does it ‘hide’ in another program, but also depends on its host to function. For the virus to run, the unsuspecting user must actively launch the infected program, which in turn launches the virus.

For this reason, virus writers usually create viruses that infect executable files (especially popular programs such as word processors or media files), which have a higher chance of being run; programs with files that get passed around a lot are extra attractive, since they can affect even more potential victims.

A good example is the Microsoft Office suite which, with their huge community of business and personal users, used to be a popular target for macro viruses. We still see queries related to this virus type, though thankfully far less than previously.

“Produces copies of itself and inserts them into other programs”

If you think of the common cold virus spreading from one person to another, you’ll have a pretty good idea of why this behavior can be so damaging. When a infected file is executed, it searches for and infects new files; if the newly infected files are launched, they find and infect new files in turn, like some evil Multi-Level Marketing operation. At worst, this pattern can lead to every targeted file on the system being infected.

“Usually performs a malicious action”

The damage a virus can do by replicating and infecting new files is bad enough; its payload, a completely separate set of nasty actions, can be worse. The range of actions a virus can take is huge – connecting to a remote site, changing the desktop wallpaper, displaying silly notification messages, deleting data files…it really just depends on the virus author’s imagination and programming skills.

If you’re lucky, they’re not that good and you get failed viruses like Virus:W32/Stardust; if they’re good, then you get really nasty beasts like Virus:W32/Virut or Virus:W32/Sality.AA (one of the few viruses we still find regularly active).

Appending, prepending, cavity…who cares?

A dialogue screen shown by Virus:W32/ZMK

With thousands of unique viruses out in the wild, antivirus companies find it necessary to divide them into sub-types. Unlike trojans though, viruses don’t fall into neat categories reflecting their actions; instead, they naturally fall into groupings based on technical differences in the way they infect a file – which is  basically gobbledeegook to a user not interested in detailed analysis.

Gnerally, viruses can be divided into two groups – system infectors and file infectors. The majority of viruses are the latter and infect programs or data files. System infectors on the other hand write their malicious code to specific, critical sections of the hard disk containing the operating system, so that while the OS is running its normal routines, it’s also unintentionally executing the virus code.

Fortunately, for most users a virus’s classification is largely academic. For better or for worse, the sheer variety of possible effects each unique virus can have on a file or system makes it more practical to take each virus on a case by case basis.

Back to what’s important – why should the user  care?

So let’s go back to the original question that sparked off this series: do you really need to know if it’s a virus – as opposed to, say, a trojan or worm – infecting your computer?

Well, it helps to know because the two malware types tend affect your data and computer in different ways. As a (very) general rule, trojan infections is more about data theft and loss of control over the computer; virus infections tend to result in software disruptions or damage.

Trojans may copy and steal your data, but they don’t usually destroy the data file itself; they may stop programs from running but they don’t destroy the program. A virus on the other hand, insert its own code into a program or data file, and depending on how it does so, may either leave the host completely unharmed and functional, slightly disrupted, or completely non-functional.

Another difference between trojans and viruses that really affects the user involves disinfection. For one thing, a trojan is usually a single, discrete program – getting rid of it tends to be fairly simple, a matter of removing the malicious file and its residuals (registry keys, processes, icons, etc). Removing the trojan also generally doesn’t affect the integrity of other files on the computer.

Viruses are far more nebulous by design – they can be present in multiple files, in different locations. Identifying a virus-infected file may require scanning the entire computer to be sure every affected file is caught. Removing malicious code from an infected file or – if it can’t be saved, deleting the infected file entirely – can also be problematic if the damaged data is important or the program is a critical system component.

And this doesn’t even take into account the virus’s payload, which can produce a whole other set of worries.

If you’re still interested

Still, there is a ray of hope. If current malware trends persist, we may soon see adware or backdoors promoted to being the newest member of The Big Three, and viruses – as a distinct malware type – can finally be relegated to joining 3½” floppy disks in Computer Hell.

In the meantime, here’s some links to other, more in-depth resources on viruses:

Or partially available on Google Books:

  • “Elements of Computer Security” by David Salomon
  • “Cybercrimes: A Multidisciplinary Analysis” by Sumit Ghosh

Next

Coming soon – Worms!

More posts from this topic

wifi_exp_cropped

The Dangers of Public WiFi – And Crazy Things People Do To Use It

Would you give up your firstborn child or favorite pet to use free WiFi? Of course not. Sounds crazy, right? But in an independent investigation conducted on behalf of F-Secure, several people agreed to do just that – just to be able to instantly, freely connect to the Internet while on the go. For the experiment, we asked Finn Steglich of the German penetration testing company, SySS, to build a WiFi hotspot, take it out on the streets of London, and set it up and wait for folks to connect. The purpose? To find out how readily people would connect to an unknown WiFi hotspot. (You can view our complete report, see the video and listen to the podcast below.) Thing is, public hotspots are insecure. Public WiFi simply wasn’t built with 21st century security demands in mind. When you use public WiFi without any added security measures, you leak data about yourself from your device. We know it, but we wanted to find out in general how well people out on the street know, whether or not they take precautions, and what kind of data they would actually leak. We also enlisted the help of freelance journalist Peter Warren of the UK’s Cyber Security Research Institute, who came along to document it all. Accompanying the two was Sean Sullivan, F-Secure’s Security Advisor. [protected-iframe id="4904e81e9615a16d107096f242273fee-10874323-40632396" info="//www.youtube-nocookie.com/embed/OXzDyL3gaZo" width="640" height="360" frameborder="0" allowfullscreen=""] Leaking personal information What we found was that people readily and happily connected, unaware their Internet activity was being spied on by the team. In just a half-hour period, 250 devices connected to the hotspot. Most of these were probably automatic connections, without their owner even realizing it. 33 people actively sent Internet traffic, doing web searches, sending email, etc. The team collected 32 MB of traffic – which was promptly destroyed in the interest of consumer privacy. The researchers were a bit surprised when they found that they could actually read the text of emails sent over a POP3 network, along with the addresses of the sender and recipient, and even the password of the sender. Encryption, anyone? If you aren’t already using it, you should be! The Herod clause For part of the experiment, the guys enabled a terms and conditions (T&C) page that people needed to agree to before being able to use the hotspot. One of the terms stipulated that the user must give up their firstborn child or most beloved pet in exchange for WiFi use. In the short time the T&C page was active, six people agreed to the outlandish clause. Of course, this simply illustrates the lack of attention people pay to such pages. Terms and conditions are usually longer than most people want to take time to read, and often they’re difficult to understand. We, of course, won’t enforce the clause and make people follow through with surrendering their loved ones – but this should give us all pause: What are we really signing up for when we check the “agree” box at the end of a long list of T&C’s we don’t read? There's a need for more clarity and transparency about what's actually being collected or required of the user. The problem So what’s really the issue here? What’s going to happen to your data, anyway? The problem is there are plenty of criminals who love to get their hands on WiFi traffic to collect usernames, passwords, etc. It’s easy and cheap enough for them to set up their own hotspot somewhere (the whole hotspot setup only cost SySS about 200 euros), give it a credible-looking name, and just let the data flow in. And even if a hotspot is provided by a legitimate business or organization, criminals can still use “sniffing” tools to spy on others’ Internet traffic. So be warned: Public WiFi is NOT secure or safe. But we’re not saying don’t use it, we’re saying don’t use it without proper security. A good VPN will provide encryption so even if someone tries, they can’t tap into your data. The Solution F-Secure Freedome is our super cool, super simple wi-fi security product, or VPN. Freedome creates a secure, encrypted connection from your device and protects you from snoops and spies, wherever you go and whatever WiFi you use. (Bonus: It also includes tracking protection from Internet marketers, browsing protection to block malicious sites and apps, and lets you choose your own virtual location so you can view your favorite web content even when you’re abroad.) Still don’t believe that public WiFi poses risks? Take a closer look next time you’re faced with a terms and conditions page for public WiFi hotspot. “A good number of open wi-fi providers take the time to tell you in their T&C that there are inherent risks with wireless communications and suggest using a VPN,” Sullivan says. “So if you don't take it from me, take it from them.”   Check out the full report here (PDF): Tainted Love - How Wi-Fi Betrays Us   Listen to the podcast, featuring interviews with Victor Hayes, the "Father of WiFi," our Sean Sullivan and others: [audio mp3="http://fsecureconsumer.files.wordpress.com/2014/09/wifi_experiment_podcast.mp3"][/audio]   Disclaimer: During the course of this experiment, no user was compromised at any point nor user data exposed in a way that it could have been subject to misuse. We have not logged any user information, and during the experiment a lawyer supervised all our activities to avoid breaching any laws.   Video by Magneto Films    

Sep 29, 2014
bash

Shellshock only concerns server admins – WRONG

Yet another high-profile vulnerability in the headlines, Shellshock. This one could be a big issue. The crap could really hit the fan big time if someone creates a worm that infects servers, and that is possible. But the situation seems to be brighter for us ordinary users. The affected component is the Unix/Linux command shell Bash, which is only used by nerdy admins. It is present in Macs as well, but they seem to be unaffected. Linux-based Android does not use Bash and Windows is a totally different world. So we ordinary users can relax and forget about this one. We are not affected. Right? WRONG! Where is your cloud content stored? What kind of software is used to protect your login and password, credit card number, your mail correspondence, your social media updates and all other personal info you store in web-based systems? Exactly. A significant part of that may be on systems that are vulnerable to Shellshock, and that makes you vulnerable. The best protection against vulnerabilities on your own devices is to make sure the automatic update services are enabled and working. That is like outsourcing the worries to professionals, they will create and distribute fixes when vulnerabilities are found. But what about the servers? You have no way to affect how they are managed, and you don’t even know if the services you use are affected. Is there anything you can do? Yes, but only indirectly. This issue is an excellent reminder of some very basic security principles. We have repeated them over and over, but they deserve to be repeated once again now. You can’t control how your web service providers manage their servers, but you can choose which providers you trust. Prefer services that are managed professionally. Remember that you always can, and should, demand more from services you pay for. Never reuse your password on different services. This will not prevent intrusions, but it will limit the damage when someone breaks into the system. You may still be hurt by a Shellshock-based intrusion even if you do this, but the risk should be small and the damage limited. Anyway, you know you have done your part, and its bad luck if an incident hurts you despite that. Safe surfing, Micke   PS. The best way to evaluate a service provider’s security practices is to see how they deal with security incidents. It tells a lot about their attitude, which is crucial in all security work. An incident is bad, but a swift, accurate and open response is very good.   Addition on September 30th. Contrary to what's stated above, Mac computers seem to be affected and Apple has released a patch. It's of course important to keep your device patched, but this does not really affect the main point of this article. Your cloud content is valuable and part of that may be on vulnerable servers.  

Sep 26, 2014
BY Micke
Screen Shot 2014-09-20 at 9.12.30 AM

GameOver ZeuS: The Kind of Game You Don’t Want On Your Computer

Unlike Team Fortress 2 or Doom, two of the most popular PC games of all time, GameOver ZeuS is not a game you can buy online or would willingly download on to your computer. What is GameOver ZeuS? While we’ve talked about banking Trojans before, none have been as detrimental to users as the GameOver ZeuS or GOZ Trojan, which initially began infecting users in 2012. Gameover ZeuS is designed to capture banking credentials from infected computers, and make wire transfers to criminal accounts overseas. It was allegedly authored by Russian hacker Evgeniy Bogachev, who then implanted it on computers all around the world; building a network of infected machines - or bots - that his crime syndicate could control from anywhere. It’s predominately spread through spam e-mail or phishing messages. So far, it’s been estimated to scam people out of hundreds of millions of dollars and it’s only getting worse. It doesn’t stop there; Gameover ZeuS can also be modified by hackers to load different kinds of Trojans on to it. One such Trojan is a ransomware called CryptoLocker, which is a devastating malware that locks a user’s most precious files by encrypting all the files until he or she pays the hacker a ransom. In June 2014, the FBI, Europol, and the UK’s National Crime Agency announced they had been working closely with various security firms and academic researchers around the world and took action under a program dubbed “Operation Trovar.” This initiative temporarily disrupted the system that was spreading the Trojan and infecting computers, allowing a temporary pause in additional computers from being infected. However, computers that were already infected remained at risk, as they were still compromised. What’s next? The disruption of the GameOver ZeuS botnet was a great success in many ways, but it’s not over. Our security advisor, Sean Sullivan, worries that this temporary disruption was actually more dangerous than completely taking it down. “Without arresting Bogachev, Gameover ZeuS is still a huge threat and likely to evolve to become more dangerous. The hackers can just as easily program a future version of the Trojan to initiate a “self-destruct” order (like destroy every file on a computer) if the ransom isn’t paid, or if authorities try to intervene.” What can we do to protect our digital freedom? Beware of malicious spam and phishing attempts — don’t open any attachments within emails unless you are specifically expecting something. Check email attachments carefully, and make sure you don’t open any files that automatically launch, which frequently end in .exe Have an Internet security solution in place and keep it up to date Keep your Windows operating system and your Internet browser plugins updated Back up all of your personal files regularly Also, check your machines to be sure you do not carry the Gameover ZeuS Trojan. For more information on how this powerful Trojan works and how it is spread, check out this this video. [protected-iframe id="888198d18fd45eae52e6400a39fb4437-10874323-9129869" info="//www.youtube-nocookie.com/v/JhiPDbTIsqw?hl=en_US&version=3&rel=0" width="640" height="360"] Have more questions? Ask us here on the blog.  

Sep 20, 2014