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

FBI

No, we do not need to carry black boxes

The recent statements from FBI director James Comey is yet another example of the authorities’ opportunistic approach to surveillance. He dislikes the fact that mobile operating systems from Google and Apple now come with strong encryption for data stored on the device. This security feature is naturally essential when you lose your device or if you are a potential espionage target. But the authorities do not like it as it makes investigations harder. What he said was basically that there should be a method for authorities to access data in mobile devices with a proper warrant. This would be needed to effectively fight crime. Going on to list some hated crime types, murder, child abuse, terrorism and so on. And yes, this might at first sound OK. Until you start thinking about it. Let’s translate Comey’s statement into ordinary non-obfuscated English. This is what he really said: “I, James Comey, director of FBI, want every person world-wide to carry a tracking device at all times. This device shall collect the owner’s electronic communications and be able to open cloud services where data is stored. The content of these tracking devices shall on request be made available to the US authorities. We don’t care if this weakens your security, and you shouldn’t care because our goals are more important than your privacy.” Yes, that’s what we are talking about here. The “tracking devices” are of course our mobile phones and other digital gadgets. Our digital lives are already accurate mirrors of our actual lives. Our gadgets do not only contain actual data, they are also a gate to the cloud services because they store passwords. Granting FBI access to mobile devices does not only reveal data on the device. It also opens up all the user’s cloud services, regardless of if they are within US jurisdiction or not. In short. Comey want to put a black box in the pocket of every citizen world-wide. Black boxes that record flight data and communications are justified in cockpits, not in ordinary peoples’ private lives. But wait. What if they really could solve crimes this way? Yes, there would probably be a handful of cases where data gathered this way is crucial. At least enough to make fancy PR and publically show how important it is for the authorities to have access to private data. But even proposing weakening the security of commonly and globally used operating systems is a sign of gross negligence against peoples’ right to security and privacy. The risk is magnitudes bigger than the upside. Comey was diffuse when talking about examples of cases solved using device data. But the history is full of cases solved *without* data from smart devices. Well, just a decade ago we didn’t even have this kind of tracking devices. And the police did succeed in catching murderers and other criminals despite that. You can also today select to not use a smartphone, and thus drop the FBI-tracker. That is your right and you do not break any laws by doing so. Many security-aware criminals are probably operating this way, and many more would if Comey gets what he wants. So it’s very obvious that the FBI must have capability to investigate crime even without turning every phone into a black box. Comey’s proposal is just purely opportunistic, he wants this data because it exists. Not because he really needs it.   Safe surfing, Micke    

Oct 17, 2014
BY Micke
Screen Shot 2014-10-15 at 7.29.32 AM

Who is waging digital war on the Hong Kong protesters?

Is this China's digital riot police? A "particularly remarkable advanced persistent threat" has been compromising websites in Hong Kong and Japan for months, according to Volexity. The pro-democratic sites that have been infected include "Alliance for True Democracy – Hong Kong" and "People Power – Hong Kong" along with several others identified with the Occupy Central and Umbrella Revolution student movements behind the massive protests against the Chinese government. Visitors to the sites are being targeted by malware designed for "exploitation, compromise, and digital surveillance". In an analysis on our Labs Blog, Micke notes that it's possible that cybercriminals could be simply piggybacking on the news without any political motivation. However, the Remote Access Trojans (RATs) being used could provide serious advantages to political opponents of the movement. "A lot of the visitors on these sites are involved in the movement somehow, either as leaders or at grassroot level," he writes. "Their enemy could gain a lot of valuable information by planting RATs even in a small fraction of these peoples’ devices." And even leaders aren't compromised, the publicity around the attack will drive users away from the sites. This is a tactic that would definitely benefit those who want these see protests to end ASAP.  And it would be a far more effective tactic if not for social networks like Twitter that can be accessed to plan resistance,even if the government blocks them -- as long as you have a VPN solution like our Freedome. If the goal is to cripple the protests by targeting protesters, "you don’t have to be a genius to figure out that China is the prime suspect," Micke writes. The significance a state-sponsored RAT attack -- or even a state-condoned attack carried out by privateers -- would be immense. Criminals use malware to target individuals, businesses and governments themselves. Government-sponsored cyberattacks on citizens practicing civil disobedience could be considered an escalation beyond even likely government-sponsored surveillance malware like Flame, which forces businesses to consider malware attacks from their own governments. Over the last year we've learned just how far suspicious governments will go to play defense against internet users who haven't been accused of any crime. Now we're seeing hints that a government may be willing to play offense too.

Oct 15, 2014
Dropbox

The Dropbox password leak – 6 lessons we learned

Yet another massive user ID and password leak. This time it affects about 7 million DropBox users, even if DropBox denies they were hacked. As usual, such a hack means that the data these users have stored in DropBox is in jeopardy. It also means that those who use the same ID and password on many services have much bigger troubles. Let’s see what we can learn from this: Always use unique passwords on the services you use. This does not prevent password leaks, but it limits the damage when a leak occur. (A password manager you trust makes this much easier.) Be alert and change your password as soon as you hear about a leak like this. Right now, we don’t know which users are affected. But if you have an old and weak password, it’s a good idea to change it NOW anyway. Changing it one time too many is better than having your confidential data all over the Internet. Pay attention to the security-awareness of the cloud providers you use. This may not have been DropBox’s fault, but it could have been. This is a good opportunity to mention our own younited, which is built with security in mind from the ground up, and is located in a country where the authorities doesn’t do mass surveillance. BTW, Edward also thinks you should consider alternatives to DropBox. DropBox claims this leak happened in some other service that connect to DropBox. This is a plausible explanation and reminds us about the danger of connecting services to each other. If you enter the password of any service into another service, you must ask yourself two questions. Will this company refrain from misusing my data and does this company protect my password sufficiently? By replicating the password to several places you increase the risk that it leaks out. Don’t do that unless you get a significant benefit and trust all places where the password is stored. Two-factor authentication is a great feature that increase security. Use it whenever possible. It should by now be clear that this kind of massive password leaks aren’t rare incidents. We see a constant stream of these and there are probably many leaks that remain unnoticed, or are noticed but stay out of the headlines. We all have to realize that a leak like this will hit us sooner or later. Sorry for sounding like a broken record, if you still have the same password on several services, you should be busy changing them by now. Safe surfing, Micke Image: Screen capture from dropbox.com   PS. Isn't that screenshot a bit funny? Yes, your data in DropBox could really be ANYWHERE right now.  :)  

Oct 15, 2014
BY Micke